1. Preheat your oven to 375 F (190 C). Lightly spray a 12-cup standard muffin tin with non-stick cooking spray. Unroll the crescent roll dough and separate it into 8 triangles. Cut each triangle in half lengthwise, creating 16 smaller triangles. Press two small triangles into each muffin cup, overlapping slightly to form a cup shape, making sure the dough covers the bottom and sides.

2. In a medium saucepan over medium heat, melt the butter. Once melted, sprinkle in the flour and whisk continuously for about 1 minute until a smooth paste (roux) forms.

3. Gradually whisk in the milk, a little at a time, ensuring there are no lumps. Continue to whisk until the mixture thickens slightly, about 2-3 minutes. Remove the saucepan from the heat and stir in the mashed butternut squash, shredded cheddar cheese, Parmesan cheese, salt, pepper, and optional nutmeg. Stir until the cheeses are fully melted and the sauce is smooth and creamy.

4. Carefully spoon the butternut squash cheese mixture into each crescent roll cup in the prepared muffin tin, filling them almost to the top.

5. Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the crescent dough is golden brown and the cheese sauce is bubbly and slightly set.

6. Once baked, remove the muffin tin from the oven. Let the cups cool in the tin for about 5-10 minutes before carefully removing them. This cooling time helps them set and makes them easier to handle without falling apart.