Preheat your oven to 350°F (175°C) and line your cookie sheets with parchment paper or leave them ungreased.

In a large mixing bowl, beat the softened unsalted butter with white sugar until creamy and light, about 2-3 minutes.

Mix in the baking powder, baking soda, salt, and ground cinnamon until well combined.

Add the eggs and vanilla extract, beating until smooth and glossy.

Gently incorporate the pumpkin puree until fully mixed.

Gradually mix in the all-purpose flour just until combined, creating a thick, sticky dough.

Drop heaping teaspoons of dough onto prepared cookie sheets, spacing them about 2 inches apart.

Bake for 10-12 minutes until the tops are set and lightly spring back when touched.

Cool the cookies on the sheets for about 5 minutes before transferring them to wire racks.

To make the frosting, melt butter with light brown sugar in a saucepan and whisk in the milk and vanilla, then beat in confectioners' sugar until smooth.

Frost cooled cookies generously with brown sugar frosting and sprinkle with ground cinnamon if desired.