1/3 cup sliced almonds, plus more for pressing on top
Melt 4 tbsp of butter in a small saucepan over medium-low heat. Once melted, add rosemary, and continue to stir until butter bubbles and crackles, then turns a rich medium brown. For a stronger brown butter flavor, let the butter go darker (even burned). Set aside and let cool.
Sift together cake flour, bread flour, baking soda, baking powder, and salt.
In a large bowl, cream together the brown sugar and remaining 6 tbsp of softened butter until smooth. Add the granulated sugar, then set a fine mesh strainer over the bowl and pour the browned butter through, straining out the rosemary sprigs. Discard sprigs, then beat again vigorously until mixture becomes light and fluffy, about 2 minutes. Finally, add the egg, almond extract, and vanilla extract, and beat again until incorporated.
Add the dry ingredients to the wet and mix gently just until incorporated. Finally, fold in the white chocolate and almonds.
Chill the dough for at least 4 hours and ideally up to 36 hours.
When you’re ready to bake, preheat the oven to 350 degrees. Roll the dough into balls of about two tablespoons each, and place on a parchment- or Silpat-lined baking sheet about 3 inches apart. If you like, press a few more almonds on top. Bake for 15-20 minutes, or until edges are set and centers are still soft. Cookies will continue to set once they’ve been removed from the oven.