Scalloped Potatoes and Bacon (Milk, Cheddar and Chives)

Imagine a loaded baked potato topped with bacon, Cheddar and chives combined with the creamy goodness of scalloped potatoes, and you have the ultimate comfort food casserole.

2½ lbs Yukon Gold potatoes, cut into ¼" slices (~ 8 cups)
1 Tbsp. extra-virgin olive oil
3 strips center-cut bacon (~ 2 oz), chopped
1 small onion, finely chopped (~ 1 cup)
3 Tbsp. all-purpose flour, unbleached
½ tsp. sea salt
¼ tsp. white or black pepper, freshly cracked
2½ cups milk
½ cup extra-sharp cheddar cheese, shredded, divided
¼ cup fresh chives, chopped, divided

Preheat an oven to 425°F (220°C/200°C fan, Gas Mark 7). Position racks in upper and lower third of oven.

Toss potatoes with oil in a large bowl until well coated. Divide between 2 large rimmed baking sheets and spread in an even layer. Roast, rotating the pans from top to bottom about halfway through, until tender and beginning to brown, 20-25 minutes.

Meanwhile, cook bacon in a large saucepan over medium heat, stirring frequently, until just crisp, about 3 minutes. Remove the bacon with a slotted spoon to a paper towel-lined plate. Add onion to the pan; cook, stirring frequently, until very soft and golden brown, 5-8 minutes. Add flour, salt and pepper; cook, stirring, for 1 minute more. Add milk; cook, stirring and scraping up any brown bits at the bottom of the pan. Increase heat to medium-high; cook, stirring, until the sauce thickens and bubbles, 3-5 minutes. Remove from heat.

When the potatoes are done, remove them from the oven. Preheat the broiler.

Transfer half the potatoes to a 2 qt broiler-safe baking dish. Spread half the sauce over the potatoes and top with ¼ cup cheese and 2 Tbsp. chives. Add the remaining potatoes, sauce and cheese.

Top with the bacon. Broil, watching carefully, until the sauce is bubbling and the cheese is beginning to brown, 1-5 minutes depending on your broiler. Let stand for 10 minutes. Serve topped with the remaining 2 Tbsp. chives.