Step 1

Make batter: Whisk together the flour and salt in a large bowl. Form a well in the center. Add the milk, melted butter, and eggs and beat until the batter is completely smooth (no lumps), the consistency of whipping cream.Let sit for an hour.

Step 2

Preheat baking dish with drippings: Heat oven to 450°F. Add roast drippings to a 9x12-inch pyrex or ceramic casserole dish, coating the bottom of the dish. Heat the dish in the oven for 10 minutes.For a popover version you can use a popover pan or a muffin pan, putting at least a teaspoon of drippings in the bottom of each well, and place in oven for just a couple minutes.

Step 3

Pour batter into dish, bake: Carefully pour the batter into the pan (or the wells of muffin/popover pans, filling just 1/3 full), once the pan is hot.Cook for 15 minutes at 450°F, then reduce the heat to 350°F and cook for 15 to 20 more minutes, until puffy and golden brown.Cut into squares to serve.