Place the diced peaches in a medium saucepan along with the brown sugar, ground cinnamon, nutmeg, lemon juice, and the cornstarch slurry. Set the pan over medium heat and let the mixture simmer for approximately 5 minutes, stirring consistently to avoid sticking or burning. The mixture should become thick and syrupy. Stir in vanilla. Set aside to cool completely.

Step 2: Prepare the Crumble Topping

In a small bowl, combine flour, brown sugar, granulated sugar, and cinnamon. Stir in melted butter until crumbs form. Set aside.

Step 3: Mix the Cookie Dough

In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until fluffy. Beat in eggs one at a time, then mix in vanilla.

In a separate bowl, whisk together flour, baking soda, baking powder, cinnamon, and salt. Gradually add dry ingredients to the wet mixture. Stir until fully combined. Chill dough in the fridge for 30 minutes.

Step 4: Assemble and Bake

Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper. Portion out about two tablespoons of dough for each cookie and arrange them on the baking sheet, ensuring at least two inches of space between each to allow for spreading.

Make a small indentation in each ball with the back of a spoon. Fill the center with a spoonful of cooled peach filling and sprinkle crumble topping over each.

Bake for 10–12 minutes or until edges are golden. Cool on the tray before transferring to a rack.

Step 5: Optional Glaze

Whisk together powdered sugar, milk, and vanilla extract. Drizzle over cooled cookies for added sweetness.