Didn't have mashed potatoes so tried this.

Preheat oven to 400f
3 cups water
1 package Lipton beef onion soup mix
3 tablespoons corn starch
2 cups pre-cooked ground beef
1 cup frozen mixed vegetables
1 cup frozen Obrien potatoes
Bisquick biscuit mix

Combine all but the biscuit mix in a saucepan
simmer stirring occasionally till it thickens about (10 minutes after starting to simmer)
Mix the Bisquick per instructions for Biscuits. Using more Bisquick knead till no longer sticky and roll out to 1/8" thick, Cut to fit an 8 by 10" casserole dish
Pour the ingredients into the dish and top with the rolled out biscuit cutting vents and bake for 30 minutes