In a medium skillet, heat olive oil over medium heat. Add thinly sliced onions and pinch of salt. Cook onions for 30 minutes, or until onions are browned and caramelized.

While the onions are cooking, pre-heat oven to 400F. Place cubed butternut squash on a baking sheet and toss with a teaspoon of olive oil and sprinkle with salt and pepper. Roast for 15 minutes, or until soft. Remove and set aside.

When onions are caramelized, add broccolini and cremini mushrooms and sauteé for 5-10 minutes. Add garlic to the top and cook just until fragrant.

Lightly flour your work surface and roll out pizza dough to a 1/8-inch thick circle. Transfer pizza dough to a piece of parchment. Add the tomato sauce to one half. Top with broccolini/mixture. Add the butternut squash and then finish it off with a few slices of mozzarella.

Fold dough in half, over filling, and crimp as desired to seal. Transfer parchment with calzone to a baking sheet. Using a knife, slice a hole in the top. This will allow steam to escape as it bakes. Place it in the oven and cook until dough is puffed up and golden brown, 15-20 minutes.