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.