Place popover pan or regular muffin pan on a lower to middle rack in the oven. Ensure that any rack above the pan is set high enough, so the rising popovers won't hit it. Preheat oven and pan to 450° F while preparing the popover batter.

In a medium bowl, lightly whisk the eggs, just until streaks of yolks and whites disappear. If you have a bowl with a spout or a large liquid measure, that works really well for pouring the finished batter into the cups of the popover/muffin pan.

Add milk, sourdough starter or discard, and salt. Whisk lightly, just to combine.

Gently whisk in the flour until large lumps disappear, taking care to not overmix. A few small lumps are ok. The batter will be very thin, about the consistency of heavy cream.

Once popover pan or muffin pan has been heated, very carefully remove it from the oven and quickly spray it with nonstick spray.

Divide batter evenly between cups. If your bowl doesn't have a spout, a ladle also works well. For a popover pan, fill each cup about half-way. For a muffin pan, fill each cup almost to the top. Muffin pans have smaller cups, so you will have enough batter to make 8 (smaller) popovers.

Place pan in oven and bake for 15 minutes at 450° F. Then reduce heat to 375° F and bake for an additional 15 to 20 minutes, until popovers are golden brown. The popovers will be more stable the longer they are baked, so I bake them as long as possible without letting them get too dark. Remove pan from oven and pierce each popover once with a sharp knife tip to release steam.

Serve immediately with softened butter (I recommend salted butter OR unsalted butter with a little sprinkle of salt!) or whipped Cinnamon Honey Butter. >>> Fluffy Whipped Blueberry Butter, Fluffy Whipped Pumpkin Pie Spice Butter, and Whipped Lemon-Vanilla Bean Butter are also wonderful!