Begin by ensuring your unsalted butter is softened to room temperature, then beat into a creamy texture for about 3 minutes until light and fluffy.

Gradually sift in the powdered sugar while mixing on low speed to prevent a sugary cloud. Beat on medium until fluffy and light for 2-3 minutes.

Add molasses and ground cinnamon, mixing on low speed for 1-2 minutes until integrated.

Gradually add milk to achieve desired frosting consistency, mixing until creamy and glossy, about 1-2 minutes.

Blend in vanilla extract on low speed for about 30 seconds, tasting for balance of sweetness and spice.

Spread the frosting over the cooled gingerbread cake using a spatula to create decorative swirls.

Add optional decorations like sprinkles or nuts, serve immediately, and store leftovers in an airtight container.