3 cups unbleached all-purpose flour, plus more for rolling out the dough
2 1/2 tsp baking powder
1/2 tsp baking soda
1/2 tsp sugar
1/2 tsp fine sea salt
3/4 cup cold, unsalted butter, cut into 1/2-inch pieces
3/4 cup buttermilk
1/2 cup half-and-half, plus more for brushing on the biscuits

1. Position rack in the center of the oven and preheat to 400 degrees. Line a large rimmed baking sheet with parchment paper.
2. Sift the flour, baking powder, baking soda, sugar and salt together into a medium bowl. Add the butter and toss to coat with flour mixture. Using a pastry blender or two knives, cut in the butter until the mixture is crumbly, with some pea-size pieces of butter. Whisk the buttermilk and half-and-half together. Make a well in the center of the flour mixture and add the buttermilk mixture. Stir to thoroughly moisten the dry ingredients, including any crumbly bits in the bottom of the bowl. (You may not use all of the liquid.) Knead the dough in the bowl just a few times, until it comes together into a moist dough.
3. Turn out the dough into a floured work surface. Dust the top with flour. Pat or roll the dough about 3/4 -inch thick. Using a biscuit cutter, cut out biscuits and place them about 1 inch apart on the lined baking sheet. Gather up the scraps, gently knead together. Repeat. Cut until the dough is done. Brush the tops of the biscuits lightly with half-and-half.
4. Bake until the biscuits are golden brown on the top and bottom, 20-25 minutes. Serve warm. The biscuits are best the day they are baked.