How to Make It
Heat oven to 400° F. Brush the cups of a 12-cup nonstick muffin tin with butter.
In a large bowl, whisk together the flour, milk, eggs, butter, and salt until only a few lumps remain (do not overmix).
Divide the batter among the prepared muffin cups and bake until puffed and a deep golden brown, 30 to 35 minutes. (Do not open oven door before 30 minutes or the popovers will collapse. Remove 1 popover to check that the underside is browned.) Serve immediately.