Begin by placing 1 cup of softened unsalted butter in a large mixing bowl. Using an electric mixer, beat the butter on medium speed until it becomes smooth and creamy, which should take about 2-3 minutes.

Gradually sift in 4 cups of powdered sugar while continuing to mix on low speed. Once incorporated, increase the speed to medium and beat until the mixture is fluffy, usually 3-5 minutes.

Add 1/2 cup of rich molasses to the fluffy mixture. Blend until the molasses is fully combined, taking care to scrape down the sides of the bowl.

Sprinkle in 2 teaspoons of ground cinnamon and 1 teaspoon of vanilla extract. Continue to mix on medium speed until the spices are well distributed.

To achieve the desired frosting consistency, gradually add 1/4 cup of milk while mixing, adding more if too thick.

Give your frosting a final mix on medium speed for about a minute. Taste and adjust flavors as desired.

Once frosted, slice your delicious creation into squares and serve at room temperature.

Store any leftover frosting in an airtight container in the refrigerator for up to a week.