I don't keep cans of frosting around. My favorite go-to quick fudge recipe. I've never tried this without the cocoa, but it might produce a decent vanilla fudge. Virtually all the vanilla fudge recipes I find call for marshsmallow fluff (or marshmallows), which I also don't keep in the house.
Quick Fudge
Adapted from the recipe on the Dominos Powdered Sugar box. This fudge always works out just right.
1 lb powdered sugar (3 ½ cups)
2/3 cup cocoa
¼ tsp salt
8 tbsp butter or margarine (1 stick)
3 tbsp evaporated milk
1 tbsp vanilla
1 cup chopped nuts
Combine all ingredients except nuts in the top of a double boiler. Place over simmering water. Stir until smooth. Add nuts and mix. Spread fudge quickly in buttered 9x5” loaf pan. Cool. Cut. Serve.