Preheat oven to 375 F. Line a baking sheet with parchment paper. In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, ginger and nutmeg; set aside. In the bowl of an electric mixer, cream together butter and brown sugar on medium speed until light and fluffy, about 3 minutes. Beat in eggs until combined.

Reduce mixer speed to low and add pumpkin, half-and-half, and vanilla. Beat until very well blended, about 2 minutes. Keep mixer on low and gradually add dry ingredients, mixing until just combined. Use a rubber spatula to give it a final mix, incorporating any flour on the sides and scraping the bottom of the bowl.

Use a large cookie scoop to form balls and place onto baking sheets, 1½ inches apart. Bake 12-15 minutes, or until the tops of the cookies spring back when lightly pressed. Cool cookies cool 5 minutes on baking sheet then remove to a wire rack to cool completely.

Butter Icing: Add powdered sugar to a heatproof bowl. Put butter in a small saucepan over medium heat and let it start melting. Continue cooking, swirling occasionally, until butter becomes golden brown and smells nutty. Remove from heat and pour over powdered sugar, scraping the browned bits from the bottom of the pan. Add half-and-half and vanilla and stir until the icing is smooth. Using a small offset spatula, spread icing on each cookie. If the icing stiffens, stir vigorously to lighten it up.