Make batter: In a blender blend batter ingredients until smooth and transfer to a bowl. Let batter stand, covered, 1 hour.
Preheat oven to 425 degrees. Spoon 1 teaspoon roast drippings into each cup of 3 mini muffin pans. Put 2 mini-muffin pans on 1 baking sheet and put remaining pan on another baking sheet. Put first baking sheet with the two mini muffin pans in middle of oven for 3 minutes to heat drippings in cups. Working quickly, pour 2 teaspoons of batter into hot drippings in each cup and bake in middle of oven 18 minutes, or until pudding shells are golden and puffed. Remove shells from cups with tongs and cool on racks. Repeat procedure with other baking sheet. Shells may be made 3 days ahead and chilled, covered, or 1 month ahead and frozen in airtight containers. Bring shells to room temperature and re-crisp in a 300 degree oven 10 minutes.
Recipe courtesy of Sara Moulton