In a light-colored saucepan, melt 1 cup unsalted butter over medium heat, whisking constantly until foam subsides and amber specks form, about 5–7 minutes.

Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.

Whisk the browned butter with 2 cups light brown sugar and 1/4 cup granulated sugar until smooth.

Add 1 large egg and 1 teaspoon vanilla extract; whisk until combined.

Sift together 2 1/4 cups all-purpose flour, 1 teaspoon baking powder, and 1/2 teaspoon kosher salt; fold into the wet ingredients until no streaks of flour remain.

Portion dough into 2-tablespoon balls and space 2 inches apart on prepared sheets.

Bake for 12–14 minutes, rotating sheets halfway, until edges are golden and centers are set.

Cool cookies on the baking sheets for 5 minutes, then transfer to wire racks to cool completely.

In a bowl, whisk 1 cup powdered sugar with 2 tablespoons pure maple syrup and 1 tablespoon milk until thick and pourable.

Drizzle the glaze over cooled cookies and let set for 10 minutes before serving.