Melt 6 tablespoons unsalted butter, or brown all 6 tablespoons in a light-colored saucepan. Pour every browned bit into a bowl and cool slightly.

Preheat the oven to 350°F. Line 1 large baking sheet with parchment paper.

Whisk the 6 tablespoons melted butter, 1/2 cup creamy peanut butter, 1/3 cup brown sugar, 2 tablespoons granulated sugar, 1/4 cup maple syrup, 1 tablespoon milk, 1 large egg yolk, 1 teaspoon vanilla, and optional 1/4 teaspoon maple extract until smooth.

In a separate bowl, whisk 1 cup plus 2 tablespoons all-purpose flour, 1/2 teaspoon baking soda, 1/4 teaspoon baking powder, and 1/4 teaspoon salt. Stir the full dry mixture into the wet mixture just until combined.

Divide the dough into 6 portions using 1/3 cup dough per cookie. Roll each portion smooth, then shape each ball into a tall mound that stands higher than it is wide.

Roll all 6 tall mounds in granulated sugar as needed, coating them evenly without flattening their shape.

Chill the 6 shaped, sugar-coated mounds for 45 minutes to 1 hour. Arrange them on the prepared baking sheet with plenty of room between each one.

Bake the 6 chilled cookies at 350°F for 6 to 7 minutes, until the tops begin to set but still look pale.

Remove the baking sheet briefly and press a gentle crisscross into each of the 6 cookies with a fork. Keep the centers tall.

Return the 6 cookies to the 350°F oven and bake for another 4 to 6 minutes, until the edges look set and the centers remain soft and pale.

Cool all 6 cookies on the baking sheet for 10 minutes, then transfer them carefully to a wire cooling rack.