1 cup frozen light whipped dessert topping, thawed ¼ cup light sour cream Blue or green food coloring (optional)
**Test Kitchen Tip:
To make 1/2 cup sour milk, pour 1 1/2 teaspoons lemon juice or vinegar into a 1-cup glass measure. Add enough fat-free milk to make 1/2 cup total liquid; stir. (For 2/3 cup sour milk, use 2 teaspoons lemon juice or vinegar and enough fat-free milk to make 2/3 cup total liquid.) Let stand for 5 minutes before using.
Red Velvet Whoopie Pies:
Prepare as directed, except add one 1-ounce bottle red food coloring with the egg and vanilla in Step 2..
