3 cups all-purpose flour
1 tablespoon granulated sugar
4½ teaspoons baking powder
¾ teaspoon cream of tartar
¾ teaspoon salt
¾ cup buttermilk, plus more for topping
3 ounces sharp cheddar cheese, diced small
1 jalapeño, seeded and minced
3 tablespoons minced chives
¾ cup unsalted butter, cold and cut into small cubes
Coarse sea salt for topping
1. Preheat oven to 425 degrees F. Line a baking sheet with parchment paper and set aside.
2. In a large bowl, whisk together the flour, sugar, baking powder, cream of tartar and salt. In a small bowl, whisk together the buttermilk and egg. In another small bowl, toss together the cheddar cheese, jalapeño and chives.
3. Add the butter to the flour mixture and use a pastry blender (or your fingers) to work the butter into the flour until the flour resembles coarse meal with the bits of butter the size of small peas or oat flakes.
4. Toss the cheese mixture into the flour mixture. Create a well in the center of the flour mixture and add the buttermilk mixture all at once. Toss together with a fork, making sure that all of the flour bits are moistened by the buttermilk. Dump the biscuit dough onto a lightly floured surface and knead briefly, just enough to bring the dough together.
5. Pat the dough into a 1½-inch-thick circle. Using a 2½-inch circle biscuit cutter to cut the dough into rounds (or use a knife to cut them roughly into circles or squares). Gather the dough scrapes, pat into a new circle and cut more rounds. Repeat until all of the dough has been used.
6. Place the biscuits on the prepared baking sheets, brush the tops with buttermilk and sprinkle them with the sea salt. Bake for 12 to 15 minutes, or until golden brown on top. If you have leftovers, store them in an airtight container at room temperature. You can eat them straight from there the next day, or reheat in a 350-degree oven until warmed through.