Step 1: Prepare the Cookie Crust

1. Preheat oven to 350°F (175°C). Grease a 9×13-inch baking dish.

2. In a medium bowl, mix sugar cookie mix with melted butter and egg until a soft dough forms.

3. Press 2/3 of the dough firmly into the bottom of the pan to form the crust.

4. Reserve the remaining dough for later.

Step 2: Bake the Crust

1. Bake the crust for 12–15 minutes or until lightly golden.

2. Remove from oven and let it cool completely before adding the filling.

Step 3: Make the Lemon Filling

1. In a clean bowl, whisk together sweetened condensed milk, fresh lemon juice, and lemon zest until smooth.

2. Pour the lemon filling over the cooled crust, spreading it evenly.

Step 4: Whip the Cream

1. In a large mixing bowl, beat heavy whipping cream, powdered sugar, and vanilla extract on high speed until stiff peaks form.

2. Spread the whipped cream gently over the lemon layer.

Step 5: Add the Crumble Topping

1. Crumble the reserved sugar cookie dough over the whipped cream.

2. Return the pan to the oven and bake for 10–12 minutes, or until the topping is golden.

Step 6: Chill and Serve

1. Let the dessert cool, then refrigerate for at least 2 hours to set completely.

2. Slice into squares and serve chilled.