Preheat oven to 350 degrees. Line 2 baking sheets with parchment paper.

In a bowl, combine the butter, brown sugar, granulated sugar, and corn syrup and stir until blended. Stir in the oats and chopped nuts, mixing well.

Drop rounded tablespoons of the oat mixture onto the prepared baking sheets, spacing them about 2.5 inches apart.

Bake until golden brown and bubbly, about 13-15 minutes. Let cool for 5 minutes on the baking sheets. Using a metal spatula, transfer the crisps to a large flat plate or sheet of parchment to cool completely.

Meanwhile, make the filling by beating the cream, sugar and extracts with an electric mixer until stiff peaks form; set aside.

In a large mixing bowl, whisk together the pudding mix and milk until smooth. let stand 5 minutes. Fold the whipped cream into the pudding mix until well combined.

To make cookie stacks, dollop pastry cream onto a cookie, then top with berries. Repeat twice, ending with pastry cream and berries. If you want to make more servings, simply stack the cookies two high instead of three.