From 6 Bittersweets
Barely adapted from Baking with Julia via Muffins Are Ugly Cupcakes
Makes about 11 popovers (but will vary between baking pans/cups)

1 cup all purpose flour
1 cup whole or 2% milk, room temperature
1/2 tsp salt
3 eggs, room temperature
2 Tbsp unsalted butter, melted and slightly cooled

Preheat your oven to 425 degrees F. Grease your popover or muffin pan or standalone paper souffle cups.

In a large bowl, mix flour and salt together. In a small bowl, beat eggs and milk together. Add egg mixture and melted butter into flour mixture. Mix everything together well by hand or using a blender, food processor, or stand mixer. If your batter is lumpy, pour it through a strainer to remove the lumps. The batter will be quite thin, similar to the consistency of crepe batter. Pour batter into greased popover or muffin pan or standalone baking cups so that each cup is half filled. If using standalone cups, set them on a cookie sheet for baking.

Bake for 25 minutes, without opening the oven door. By that time, the popovers should have popped and should be nicely browned. At this point, lower the temperature to 350 degrees F and bake for another 15 to 20 minutes to dry out the insides. Remove from oven, let cool slightly, and enjoy with your meal!