Ingredients
Method
Plack rack in middle of oven; preheat oven to 425°. Line a rimmed baking sheet with parchment paper.
Whisk 2 cups (250 g) all-purpose flour, 2 tsp. baking powder, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a large bowl to combine. Using a pastry cutter or your fingers, work ½ cup (1 stick) chilled unsalted butter, cut into pieces into dry ingredients until mixture resembles coarse meal. Using a wooden spoon or fork, mix in ½ cup sour cream and ½ cup whole milk until a shaggy dough forms.
Turn out dough onto a lightly floured surface and knead a few times just to bring together. Roll out until ¼" thick, then fold in half. Roll dough out again until ¼" thick, then fold in half again. Repeat once more, rolling out to a ¾"-thick round.
Punch out biscuits as close together as possible with cutter. Pat scraps together and punch out more biscuits; repeat until you can’t cut out any more (you should have 12 total). Transfer biscuits to a prepared baking sheet, spacing 1" apart; bake, rotating sheet once, until golden brown and baked through, 10–12 minutes. Brush biscuits with 2 Tbsp. melted butter.
While biscuits are baking, cook 8 oz. breakfast sausage links, chopped in a medium saucepan over medium heat, stirring occasionally, until cooked through and starting to brown, 5–8 minutes. Transfer to a small bowl with a slotted spoon.
Add 2 Tbsp. unsalted butter to drippings in pan and melt over medium. Whisk ¼ cup (31 g) all-purpose flour into butter mixture and cook, whisking constantly, until roux is very smooth and starting to bubble, about 2 minutes (don’t let it color; this is a white gravy).
Gradually add 2½ cups whole milk, whisking until incorporated. Reduce heat to medium-low and cook gravy, still whisking, until thickened, 8–10 minutes. Stir in cooked sausage; season with kosher salt and a generous amount of freshly ground black pepper.
Serve hot biscuits with gravy alongside for spooning over top. Do Ahead: Biscuits can be cut out 1 day ahead. Cover and chill, or freeze up to 1 week.