Preheat the oven to 400°F. Line a baking pan with parchment paper and set aside.
Make the béchamel: Melt the butter in a large saucepan. Add the onion and cook over medium heat until soft, without letting it get color.
Add the flour and cook for 2 minutes, stirring often. Add the milk slowly while whisking. Add the nutmeg and salt. Bring to a boil while whisking; let boil for 2 minutes. Remove from heat, pour into a bowl and let cool.
Make the sauce: Add all ingredients except for the oil to a food processor and blend until combined. Slowly drizzle in the oil while the machine is running. Set aside.
Toss the broccoli with olive oil and salt and place on the prepared pan. Roast until charred and crunchy, about 20 minutes. Remove from the oven and toss with chopped basil.
Meanwhile, use a mandoline to thinly slice the garlic. Fry in olive oil until crispy and golden, then place on a paper towel-lined plate to cool.
Make the pizza: Turn the oven up to 550°F. Shape the dough into a 9- to 12-inch circle and place on a baking stone or an inverted baking sheet pan. Spread a thin layer of béchamel on top. Add the roasted broccoli and top with Provel. Add the grated cheeses, sprinkle with dried oregano and red pepper, and bake for 7 minutes. Slice, drizzle with sauce, garnish with the garlic chips and serve.