Place broccoli florets in a gallon size resealable bag, drizzle with olive oil, shake to coat. Add panko bread crumbs, parmesan cheese, and Italian seasoning; shake to coat.
Dump broccoli and crumbs onto the prepared baking sheet. Season with Kosher salt and freshly ground black pepper. Roast for 10-15 minutes, watching closely so the crumbs don’t burn.
While broccoli is roasting, add the macaroni, butter, salt, dry mustard, cayenne, garlic powder, cornstarch, 2 ½ cups of water, and only 2 cups of milk to the pressure cooker pot. Stir well, to incorporate cornstarch.