Add flour, baking powder, baking soda, beat until blended. Stir in walnuts. Dough will be sticky.
2 & 1/4 cup (285g) all-purpose flour, 2 tsp baking powder, 1/4 tsp baking soda
Using a medium cookie scoop or tablespoons, drop rounded cookie dough 2" apart onto prepared baking sheets.
Bake for 12-14 minutes or until edges start to brown. Remove cookies from baking sheets and cool on racks.
Frosting
Beat cream cheese and powdered sugar together until smooth. Feel free to add more powdered sugar if needed to suit your taste. Spread on completely cooled cookies and sprinkle with some coarse sugar if desired.
Notes
Cookies can be stored in the refrigerator in an airtight container for 2-3 days.