4 tablespoons cold, unsalted butter, cut into small cubes
1/4 cup very finely chopped scallion greens
3 ounces extra-sharp, white cheddar cheese, shredded (1 cup)
1/2 cup plus 2 tablespoons cold milk
Preheat the oven to 375°. Lightly grease two 12-cup mini-muffin tins. In a medium bowl, mix the flour, baking powder, salt and cayenne. Using 2 knives, a pastry blender or your fingers, work in the butter until the mixture resembles coarse meal with some small pieces of butter still visible. Add the scallion greens, cheese and milk and stir with a wooden spoon just until the dough comes together.
Scoop the dough into the prepared mini-muffin tins. Bake for about 25 minutes, until the muffins are lightly browned on top. Transfer the muffin tins to a wire rack to cool slightly. Serve warm.