Preheat the oven to 450°F / 230°C and line a baking sheet with parchment paper. Whisk 2 cups of all-purpose flour, 1½ tablespoons of baking powder, 1 teaspoon of sugar, and ¾ teaspoon of salt.
Add ½ cup of cold unsalted butter, diced into ½in / 1cm cubes, and cut it in with a pastry blender until the largest pieces are pea-sized. Stir in ¾ cup plus 2 tablespoons of cold half-and-half until a dough forms.
On a floured surface, pat the dough into a rectangle, fold it in half, and pat it out again. Repeat once, then pat it ¾in / 2cm thick.
Cut out biscuits with a floured 2½in / 6.5cm cutter, pressing the scraps together to cut more. Bake on the baking sheet for 12-15 minutes, until golden, and brush with a little melted butter while hot.
Meanwhile, brown 450g of breakfast sausage in 2 tablespoons of butter over medium-high heat for about 5 minutes, breaking it up. Lower the heat, stir in ¼ cup of all-purpose flour, and cook for 3 minutes.
Gradually stir in 2½ cups of milk, season with salt and coarsely ground black pepper, and simmer, uncovered, for about 5 minutes, until thick. Spoon the gravy over the split biscuits.
