Chocolate Fudge Sheet Cake (Cocoa)

chocolatefudgesheetcakecocoa Soft and super moist one bowl chocolate cake with the fudgiest rich chocolate frosting! It's so easy to make and incredibly delicious.

Chocolate Fudge Cake Batter:
1 cup all-purpose flour, unbleached (142 g)
⅓ cup cocoa powder (28 g)
½ tsp. baking powder
½ tsp. baking soda
¾ cup granulated sugar (150 g)
¼ tsp. sea salt
1 large egg
¼ cup sunflower oil (60 mL)
⅓ cup full fat sour cream (80 mL)
½ tsp. pure vanilla extract
½ cup coffee, hot (120 mL)

Chocolate Fudge Frosting:
⅓ cup 35% heavy whipping cream (80 mL)
1 Tbsp. pure honey (15 mL)
1 pinch sea salt
5 oz dark chocolate, finely chopped (142 g)
¼ cup full fat sour cream (60 mL)

Preheat your oven to 350°F (180°C/160°C fan, Gas Mark 4). Line a 9x9" square pan with parchment paper.

Make the Cake:
Sift flour, cocoa, baking powder and baking soda into a large bowl. Add sugar and salt and whisk to blend well.

Combine egg, oil, sour cream and vanilla in a medium bowl and whisk to blend until smooth. Pour into the bowl with the dry ingredients and mix with an electric hand mixer on medium-low until blended. It will be thick and somewhat dry. Add the hot coffee gradually in two stages to minimize clumps forming and beat until evenly combined and the batter smooth.

Spread batter into prepared pan and bake for 24-27 minutes until the cake springs back when pressed gently and a skewer inserted into the center comes out clean. Transfer pan to a wire rack and let cool for 15 minutes before inverting onto the rack to cool completely.

Make the Frosting:
Combine cream, honey, salt and chopped dark chocolate in a small saucepan over low heat and stir gently as the chocolate slowly melts. Keep an eye on it and let the chocolate melt slowly, then whisk gently until it is smooth and glossy. Be careful not to over-heat it.

Pour it into a bowl and add the sour cream. Stir gently with a whisk until all of the sour cream is incorporated and the mixture is smooth, then place it in the fridge for about 15 minutes to cool but not until it is firm. It should be the consistency of soft pudding. Whisk vigorously for about 20 seconds to lighten it up and use immediately. This frosting will firm up once it cools completely and sets.

Makes 12 servings.

Cook's Notes:

Use a neutral tasting oil like pure sunflower oil for the cleanest flavor to let the chocolate taste stand out.
Do not reduce the sugar: the right amount of sugar will make this cake moist because it binds water so that it stays tightly in the batter and doesn't evaporate excessively during baking.
Keep an eye on the baking time. Set a timer for the first time stated in the recipe and check with a skewer - it should come out clean.
Use the frosting while still soft. Once the chocolate in the frosting sets up, it will become firm and difficult to spread so use it right when it is at a "pudding-like" consistency. Whipping it with a whisk will help you control the amount of air that you incorporate because if you use a mixer it is so easy to over-whip which will cause it to stiffen up quickly.

Why You Will Love this Recipe:

Easy to make: this cake can be made in one bowl with a whisk. You don't need a mixer, although I often use my electric hand mixer to make it.
Moist chocolate cake: the cake is SO super moist! It has the softest texture and stays moist for days without drying out.
Fudgy chocolate frosting: I use a rich chocolate ganache made with sour cream for the frosting. It is so easy to make and you don't need softened butter nor icing sugar. It's simple and so decadent and fudgy! Many people have told me this is the best frosting they've ever made!
Small batch: this recipe makes just a one layer 9x9-inch cake so you only need one pan and it serves 9-12 people.

Ingredients:

All purpose flour: I use regular unbleached all-purpose flour to make this wonderful chocolate cake. If you'd like to use cake flour, then make sure it is also unbleached since bleached or chlorinated cake flour has completely different properties. This batter is meant to be quite runny so refrain from adding more flour to make it thicker.
Pure vanilla extract: vanilla enhances the flavor of the chocolate, so use your favorite kind but do not leave it out.
Cocoa powder: the quality of your cocoa powder will determine the taste of this cake. You can use natural or Dutch process for this recipe. I love to use this Dutch Process cocoa powder.
Sour cream: full fat sour cream adds richness and dairy notes to this cake in the absence of butter. It really makes this cake delicious, and if you can't get sour cream where you live then you can substitute with fill fat Greek yogurt. There is also sour cream in the frosting.
Oil: this is an oil-based cake. Although I LOVE BUTTER, oil makes cakes ultra moist since it is liquid at room temperature. Plus, with this intense chocolate flavor and the sour cream, you won't miss the butter.
Dark chocolate: the frosting is essentially a ganache lightened up a bit with sour cream which adds a subtle tanginess to complement the bitter chocolate. Anything between 50 and 70% cocoa solids will work, and actually I prefer something around 60% for the best flavor profile.
Honey: I use honey to sweeten the frosting just slightly and it helps give it a fudgy consistency while also giving it a shiny appearance.

Frequently Asked Questions:

What type of oil is best for chocolate cake? Firstly - use a fresh oil. Do not use anything that's been opened for a long time and when you store oil, it should be in a cool dark place. Light and heat accelerate oxidation reactions that can make the flavour turn rancid. My oil of choice for baking is sunflower oil for its clean and neutral taste, but any other oil such as Canola or safflower will do. You can even use olive oil, but keep in mind that it will add the taste of olive oil to the cake.
What is a substitute for sour cream? If sour cream is not available to you where you live, you can also make this recipe using an equal amount of full fat Greek yogurt. I have tested this and it worked well! Another suitable substitution is crème fraîche - a type of fermented dairy product somewhere between yogurt and sour cream.
Can I make this recipe without coffee? Yes! You can use hot water if you cannot drink caffeine. Or, you can use decaf coffee. You can also make instant coffee instead of brewing a fresh pot and for this I suggest using 1-2 teaspoons of instant coffee for 1 cup of hot water.
What makes this cake so moist? It's not more fat! Moisture comes from liquid, not fat. So you can add more butter and more oil, but it will really just make the cake more dense and more tender by shortening the texture. Fat will not make a cake moist as only liquids can add moisture. This cake is moist because of the amount of liquid. Liquid oil will make the texture very soft, which often gives the perception of "moistness".
What happens if I over-beat the frosting? If you over-beat the frosting, it will stiffen up and become very difficult to spread. It will essentially turn into a chocolate truffle, so it will be delicious but it will not be spreadable. I would recommend err on the side of under-beating. That's why I prefer to whip by hand with a whisk so that I can control the consistency and my strength.
What happens if my frosting stiffens up? If you over-whip the frosting or you forget about it in the fridge and it firms up too much, then you can try to save it but it will take some time. Place the bowl over a saucepan with just an inch of simmering water and stir as it melts gently and slowly. Make sure you don't over-heat it or heat it too fast because that will break the emulsion. Once it is all smooth and glossy again, you will need to start the cooling process and then whip it just before you think it's ready to spread.