How to Make It
Whisk together milk and eggs in a large bowl. Gradually whisk in flour and salt until well combined. Pour mixture through a fine wire-mesh strainer into a bowl; discard any lumps. Cover and chill batter 3 hours or up to overnight.
Place a large 12-cup muffin pan (6 ounces per cup) on middle oven rack. Preheat oven to 425°F. When oven is preheated, remove pan, and add 3/4 teaspoon beef tallow to 8 muffin cups. Return muffin pan to oven, and heat until tallow is hot but not smoking, about 6 minutes.
Pour about 1/4 cup batter into each muffin cup with hot tallow, and bake at 425°F until golden brown and puffed, 16 to 20 minutes. (Do not open oven while baking or puddings will collapse.) Using an offset spatula or a butter knife, carefully remove puddings from pan, and serve immediately.