Preheat the oven to 425 F. On a baking sheet, toss the cubed butternut squash with 1 tablespoon of olive oil plus a sprinkle of salt and pepper. Roast until the cubes are fork-tender, about 15 minutes. Set aside the squash and increase the temperature of the oven to 450 F.
Carefully clean the leek, rinsing off any dirt, then slice the white and light green parts into rings and start sauteing them with 1 tablespoon of olive oil in a skillet set over medium-high heat. Stir occasionally so they don't burn.
Trim and quarter the Brussels sprouts and add them to the pan with the leek after the leek has been cooking at least 2 minutes. Continue cooking the vegetables until the Brussels sprouts begin to brown, then remove from the heat.
Meanwhile, start frying 4 slices of bacon in a skillet over medium heat. Cook the bacon through but don't cook until crispy as it will crisp up more in the oven. Let it drain on paper towels set on top of a plate. Once it's cool enough to handle, roughly chop into bite-sized pieces.
Transfer the cooked squash to the bowl of a food processor or blender. Add 1 tablespoon of olive oil, the maple syrup, and a pinch of Kosher salt and a few grinds of fresh black pepper. Process until smooth and creamy, then measure out 1 cup worth of the puree.
Roughly chop the hazelnuts, pit and finely chop the Medjool dates, and crumble the blue cheese.
Roll the pizza dough out on a lightly floured surface into an approximate round about 12 inches in diameter. Transfer it to a pizza stone or baking sheet covered with parchment paper.
Spread the 1 cup of squash puree out over the dough, almost all the way out to the edges (add a little more if necessary). Top with the leek and Brussels sprout mixture, then the bacon, followed by the dates and hazelnuts. Sprinkle the pizza evenly with the crumbled blue cheese, then bake until the crust turns golden along the edges and the vegetables are slightly charred, about 15-18 minutes.