Meatless Meatballs (Chef John's)

I made this recipe for vegetarian meatballs to celebrate Earth Day. Thanks to a thorough browning, mushrooms provide more than enough savouriness. The garlic, cheese, and parsley do the rest. What really blew me away was how close the texture was to actual meatballs. They are officially approved for use on spaghetti.

1 Tbsp. extra-virgin olive oil
1 lb fresh white mushrooms, finely chopped
1 pinch sea salt
1 Tbsp. butter
½ cup onion, finely chopped
4 cloves garlic, minced
½ cup quick-cooking oats
1 oz Parmigiano-Reggiano cheese, very finely shredded
½ cup breadcrumbs
¼ cup flat-leaf (Italian) parsley, packed, chopped
2 large eggs, divided
1 tsp. sea salt
black pepper, freshly ground
1 pinch ground cayenne pepper
1 pinch dried oregano
3 cups pasta sauce
1 Tbsp. Parmigiano-Reggiano cheese, very finely shredded
1 Tbsp. flat-leaf (Italian) parsley, chopped

Heat olive oil in a skillet over medium-high heat. Add mushrooms to the hot oil, sprinkle with salt and cook and stir until liquid from mushrooms has evaporated. Stir butter into mushrooms, reduce heat to medium and cook and stir mushrooms until golden brown, about 5 minutes.

Stir onion into mushrooms and cook, stirring often, until onion is translucent, 5 minutes. Remove skillet from heat and stir garlic into mushroom mixture until fragrant, about 1 minute. Transfer mixture to a mixing bowl.

Mix oats into mushroom mixture until thoroughly combined. Gently stir 1 oz Parmigiano-Reggiano cheese into the mixture. Add bread crumbs, ¼ cup parsley and 1 egg; season with salt, black pepper, cayenne pepper and oregano. Mix together with a fork until crumbly. Stir in remaining 1 egg. The mixture should hold together when pressed.

Cover the bowl with plastic wrap and refrigerate at least 4 hours. For best flavour and texture, refrigerate overnight.

Preheat the oven to 450°F (230°C/210°C fan, Gas Mark 8). Line a baking sheet with a silicone baking mat or parchment paper.

Form mixture into small meatballs using a 2 Tbsp. scoop. Roll meatballs lightly between your hands until smooth, if desired; arrange meatballs on the prepared baking sheet.

Bake in the preheated oven until meatballs are lightly golden brown, 12-15 minutes.

Bring pasta sauce to a boil in a large saucepan; reduce heat to low. Gently stir meatballs into sauce until coated. Simmer meatballs in sauce until cooked through, 45 minutes to 1 hour.

Transfer to a serving bowl and garnish with 1 Tbsp. Parmigiano-Reggiano cheese and 1 Tbsp. parsley.