To make the cookies, preheat oven to 400 degrees F. Line a baking sheet with a silicone baking mat or parchment paper; set aside.
In a medium mixing bowl, sift together flour, baking powder, baking soda and salt; set aside.
In the bowl of a stand mixer fitter with the paddle attachment, cream together the butter and sour cream until light in color. Add the sugar, egg and vanilla extract. Mix until just combined. Add the dry ingredients to the wet ingredients in two additions, mixing well after each addition.
Using a small cookie scoop, form dough into 2" balls and place on a prepared cookie sheet 2 inches apart. Press the cookie balls flat with the back of a spoon or the bottom of a glass dusted with flour.
Bake cookies for 5 to 7 minutes, or until the bottom of the cookies are lightly brown. Carefully remove the cookies from the cookie sheet and let cool completely on a wire rack.
To make the frosting, cream the butter in the bowl of a stand mixer fitted with the paddle attachment. With the mixer on low speed, slowly add the confectioners' sugar. Mix until well blended. Add vanilla or coconut extract and one tablespoon of heavy cream. Blend until smooth. Add an additional tablespoon, until you reach the desired consistency. Beat on high speed until the frosting is light and fluffy, about 5 additional minutes. Spread frosting onto cookies and sprinkle with toasted coconut.
*To toast coconut, cook coconut in a skillet over medium heat, stirring frequently until the flakes are mostly golden brown.