Preheat oven to 350 degrees F
Line baking sheets with parchment paper or silicone mat
In a large bowl, whisk together flour, baking powder, baking soda and salt
In a large bowl, cream together butter, sour cream and sugar until light and fluffy
Mix in eggs and vanilla extract
Gradually add dry ingredients, scraping down the bowl after each addition, mix until well combined
Roll cookies into 2 inch balls
Dip the bottom of a glass into water and slightly flatten cookie
Bake at 8-10 minutes or until cookies are puffed slightly, set and bottoms are lightly browned
Remove from oven and transfer to wire rack
Allow cool
Frosting:
In a mixing bowl, cream butter until fluffy and smooth
Gradually add powdered sugar, alternating with heavy cream
Add vanilla extract and beat well
Add coloring of your choice or leave the frosting white
Frost cookies and add sprinkles
Store in airtight container