Preheat the oven to 450 degrees F. Cover a baking sheet with parchment paper.
Stir together the flour, sugar, baking powder, cream of tartar and salt in a large bowl. Add the butter and stir just until the pieces are coated with the flour mixture. Whisk together the milk and egg in a small bowl. Add milk mixture to the flour mixture and stir just until combined. Do not overmix the dough. Cut in the butter.
Flour your workspace. Turn the dough onto the workspace and pat into a 1/2-inch-thick slab. Using a biscuit cutter (or any round rimmed object), cut out 8 to 10 biscuits. Transfer the biscuits to the prepared baking sheet, making sure they don’t touch, and bake until they’ve risen slightly and are lightly browned around the edges, 12 to 15 minutes. Top with butter and keep warm.
For the sausage gravy: Heat a very large nonstick skillet over medium heat. Add the sausage and cook, breaking it up into small pieces, until browned, about 15 minutes. Add the cream and thyme, bring to a simmer, and simmer for 25 minutes. Stir together the cornstarch and 1 cup cold water in a medium bowl. Stirring constantly, pour the slurry into the pot. Simmer, stirring often, until the gravy thickens.
Split each biscuit in half and top with about ¾ cup of the sausage gravy. Extra gravy will keep, tightly covered, in the refrigerator for up to 7 days and in the freezer for up to 3 months.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Kelly O's Diner, Pittsburgh, PA