Begin by peeling and cubing the butternut squash, then slice the carrots and chop the potatoes into bite-sized pieces. Place all the vegetables in a large pot and cover them with vegetable broth. Bring the mixture to a gentle simmer over medium heat, cooking for 10-15 minutes until the vegetables are tender but firm. Drain and set aside as you prepare the filling.

In a medium saucepan, melt butter over medium heat. Add the chopped onions, Brussels sprouts, and minced garlic, sautéing for about 5 minutes until they are fragrant and softened. Sprinkle in salt and pepper to taste, then add flour to form a roux. Stir constantly for 2-3 minutes until the mixture is golden and bubbly, then slowly whisk in the reserved vegetable broth to thicken the filling.

Once the filling has thickened, fold in the simmered vegetables from Step 1. Stir in the half-and-half for creaminess, along with grated parmesan and a dash of nutmeg to enhance the flavors. Mix everything together until well combined, and then taste to adjust the seasoning as needed. Your Loaded Butternut Squash Pot Pie filling is now ready!

Preheat your oven to 425°F (220°C). Pour the creamy vegetable mixture into a greased baking dish, spreading it out evenly. Roll out the puff pastry over the filling, gently pressing down the edges to seal. Brush the top with an egg wash for a golden finish, then sprinkle with fresh sage and additional parmesan. Cut a few slits in the pastry to allow steam to escape while baking.

Place the assembled Loaded Butternut Squash Pot Pie in the preheated oven and bake for 30-35 minutes. Watch for the crust to puff up and turn a beautiful golden brown, while the filling bubbles delightfully beneath. The enticing aroma filling your kitchen signals that it's nearly time to enjoy this comforting dish!

Once baked, remove the pot pie from the oven and allow it to cool for about 10 minutes. This cooling period helps to set the filling. When ready to serve, garnish with additional fresh sage if you like, and ladle out generous portions of this warm, comforting Loaded Butternut Squash Pot Pie that your family will adore.