1. Preheat your oven to 375 F (190 C). Lightly grease a 9×13 inch baking dish. Unroll one can of crescent roll dough and press it firmly into the bottom of the prepared dish, making sure to seal any perforations to form a solid crust. You can let it extend slightly up the sides.

2. Peel, core, and thinly slice your apples. Aim for slices about 1/4-inch thick so they cook evenly. Place the sliced apples in a large bowl.

3. To the bowl of sliced apples, add the granulated sugar, ground cinnamon, ground nutmeg, and lemon juice. Toss everything together gently until the apples are evenly coated with the spices and sugar.

4. Pour the spiced apple mixture evenly over the crescent roll crust in the baking dish. Unroll the second can of crescent roll dough and carefully place it over the apple filling, gently stretching it to cover the entire surface. Pinch the edges of the top and bottom crusts together to seal.

5. Melt the unsalted butter and brush it evenly over the top layer of crescent roll dough. This will help create a beautiful golden-brown crust and add a rich flavor.

6. Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the top crust is golden brown and the apples are tender when pierced with a fork. You should see some bubbling around the edges.

7. While the bars are cooling slightly, whisk together the powdered sugar, milk or cream, and vanilla extract in a small bowl until smooth and pourable. If the glaze is too thick, add a tiny bit more milk; if too thin, add a little more powdered sugar.

8. Let the apple pie bars cool in the dish for at least 15-20 minutes before drizzling generously with the prepared glaze. This cooling time allows the filling to set up, making the bars easier to slice neatly. Slice into squares and serve warm or at room temperature.