Sift together flour, baking powder, and salt. Set aside. Place butter and sugar in a large bowl of an electric stand mixer and beat until light in color (2-3 minutes). Add egg, milk (or cream), and vanilla extract and beat to combine. Put mixer on low speed, gradually add flour, and beat until mixture pulls away from the side of the bowl.  Roll to 1/4 inch thickness between two sheets of parchment or wax paper. After rolling, chill the dough for at least 30 minutes to an hour.

Once the dough is well chilled and hard to the touch, cut out shapes and place them on a parchment-lined baking sheet about 1 inch apart. Bake at 375 degrees F for 6-8 minutes, rotating cookie sheet halfway through baking time. Do not overbake. The cookies will look a little underdone but that is ok. It will set up as it cools and results in a soft and chewy cookie. Let sit on baking sheet for 2 minutes after removal from oven and then move to complete cooling on wire rack.  Store in an airtight container for up to 1 week.

In a stand mixer fitted with the paddle attachment or in a large bowl using beaters, whip the butter for about 2 minutes, or until it's creamy and lightened in color. Slowly add in the powdered sugar. Add the vanilla extract and heavy cream or milk. Start with 3 tablespoons of cream/milk and add 1 more tablespoon if frosting seems too thick. Beat on medium-high for about 3-5 minutes, stopping to scrape the sides of the bowl once or twice. If using food coloring mix in. Beat on low speed for about 1 minute to help remove any air bubbles.

Decorate cookies as desired and top with sprinkles.

Enjoy!