Add evaporated milk, milk and flour to a saucepan. Whisk vigorously while it heats to boiling. Mixture will be thick. Remove from heat and allow to cool to room temperature.
Once cooled, whip your butter, sugar and vanilla until light and fluffy.
Add your cooled mixture and blend well until your frosting doubles in size, ~10 minutes.
To color, use food coloring in spring colors to match your cookies.
Recipe by A Day in Motherhood at https://www.adayinmotherhood.com/double-decker-chocolate-chip-spring-cookies/