Beat the butter with the margarine and add the sugar, milk, and vanilla.

Beat them at medium speed until well combined. Beat for another minute until the mixture becomes creamy. The more you beat it, the fluffier it will become.

You can color the cream by adding drops of food coloring. Divide the cream into bowls based on how many colors you want, add color to each bowl, and mix. It's best to use paste colors so they don't thin the cream.

This recipe yields 3 cups of stiff cream. With stiff cream, you can make flowers that need their petals to stand upright. If it's not stiff enough, the petals will fall. If you notice the cream 'breaks' as you pipe it, it's probably too stiff.

For medium-stiff cream, add 1 teaspoon of milk per cup of cream. With medium-stiff cream, you can make most designs with a piping bag (stars, petals, shells, etc.).

For thin cream, add 2 teaspoons of milk per cup of cream. With thin to medium cream, cover cakes. With thin cream, make designs like leaves and write with a fine tip. Otherwise, the leaves and letters will break.

In general, if your cream is too stiff, add liquid; if it's too thin, add powdered sugar.