Preheat the oven to 450 degrees F.
Put the flour, baking powder, and salt in a food processor and pulse briefly to mix. Add the butter and pulse until the mixture is crumbly. Add green onion and Parmesan and pulse just enough to blend. Add the milk and pulse until combined. Drop the dough in rounded tablespoons onto a greased baking sheet, and bake until golden, about 13 to 15 minutes.