In a large mixing bowl, beat the softened butter using a stand mixer or hand mixer until it is smooth and pale, about 2-3 minutes.

Slowly add the powdered sugar one cup at a time, mixing on low speed until incorporated. The mixture may look crumbly at first.

Pour in the heavy cream, peppermint extract, and salt. Continue mixing on low speed until a dough forms. If it's too sticky, add a little more sugar; if too dry, add a teaspoon of cream.

Turn the dough out onto a surface lightly dusted with powdered sugar. If using food coloring, divide the dough and knead in a tiny drop to each portion until uniform.

Take a small piece of dough and roll it into a long, thin rope about the thickness of a pencil.

Use a sharp knife to cut the rope into small, half-inch pieces.

Transfer the mints to a parchment-lined baking sheet. Let them air dry for at least 24 to 48 hours, or until the outside develops a slight crust while the inside remains soft and creamy.