In a large bowl, cream together butter and sugar. Add eggs and vanilla extract and beat until fluffy, about a minute.
In a separate bowl, sift together the flour, baking powder, and salt. Gradually stir dry ingredients into butter mixture until just combined.
Cover bowl or wrap dough in wax paper. Chill for at 1 hour (up to 24 hours) in the refrigerator. Refrigerating will help the flavors meld and also create a firmer dough to roll into balls.
Preheat oven to 350 degrees.
Remove dough from refrigerator and allow to sit at room temperature for 10 minutes. Scoop dough using a 1.5 tablespoon scoop or shape by hand into 1.5 inch balls.
Place cookie dough balls 2 inches apart onto a parchment lined baking sheet. Flatten the balls slightly using your hands or the bottom of a glass dusted with flour (to prevent sticking). This will ensure your cookies spread and leave you with a nice flat top to frost. Optionally, not flattening dough will give you a thicker, rounded top cookie.
Bake for 10-12 minutes, or until edges begin to barely brown. Allow to cool for 5 minutes before removing to a wire rack to cool completely.
In a medium bowl, combine butter, confectioner's sugar, and vanilla extract. Add heavy cream one tablespoon at a time, or until desired consistency is achieved. Whip until frosting is smooth and spreadable.
Decorate cookies as desired - spread with a knife or use a piping bag with decorating tip. Cookies shown are piped with a rosette using a Wilton 2D tip.
Use the spoon and level method when measuring flour to prevent thick, cakey cookies. Spoon flour into your measuring cup, then level off with a knife. Scooping flour with your measuring cup will add up to 25% extra flour to your recipe, resulting in dry cookies that won't spread.
Cookie dough will keep in refrigerator for 2-3 days, or up to 3 months in the freezer.
Cookies will keep for up to 5 days in a tightly sealed container at room temperature. Add a slice of bread to cookie container to help keep cookies moist. Replace as needed (bread will dry out).
If not frosting sugar cookies, I suggest rolling in granulated sugar before baking. Without frosting, cookies are not very sweet on their own.