Heat your oven to 400°F (200°C). Coat the cubed squash with olive oil and spread in a single layer on a baking sheet. Trim roughly ½ inch from the top of each garlic head to reveal the cloves, drizzle the exposed surfaces with a bit of olive oil, then place them cut-side down on the same sheet. Roast for 20 minutes, checking the squash for tenderness. When it's soft, remove it to a bowl and set aside. Let the garlic continue roasting for about 10 more minutes until the cloves are soft and aromatic.

Once the garlic has cooled slightly, squeeze the cloves from their skins. Use a fork to mash 10 of the cloves into a smooth paste in a small bowl. Reserve the remaining whole cloves separately—you'll use the paste for the sauce and the whole cloves as a topping.

As the squash and garlic roast, heat the butter and olive oil in a large pan over medium heat. Add the sliced onion and cook, stirring now and then, until it softens and becomes translucent. Turn the heat down to medium-low, stir in the maple syrup, and keep cooking until the onions turn light golden brown and fully caramelized, roughly 15 to 20 minutes total. Set aside.

In a frying pan or small pot over medium heat, melt the butter. Whisk in the flour and cook for about a minute to remove the raw flour flavor. Slowly add the milk while whisking constantly, then bring the mixture to a gentle boil and continue whisking until it thickens. Take the pan off the heat and stir in the mashed garlic paste. Season with salt and pepper as needed.

On a lightly floured work surface, shape each dough ball into your preferred size and thickness. Spread the white sauce evenly over both dough rounds. Layer the caramelized onions, roasted squash, whole garlic cloves, baby spinach, and goat cheese chunks evenly across each pizza, then scatter the minced rosemary over the top.

Bake each pizza individually in the preheated 400°F (200°C) oven for 12 to 15 minutes, until the crust turns golden and the cheese is bubbling with light browning. Allow the pizzas to rest for a few minutes before slicing and serving.