Place pizza stone on top rack in oven and preheat to 500 degrees.
Place sauté pan over medium heat and add ½ the oil. Add onion. Season with salt and pepper and sauté until translucent. Reduce heat to low and cook until caramelized to dark brown, about 30–45 minutes.
Place another sauté pan over medium heat and add remaining oil. Add mushrooms and cook until lightly browned, about 5 minutes. Fold ½ the caramelized onions and thyme into mushrooms.
Form dough ball into pizza using traditional “slap” method. To do this, make 2 fists and place dough on top. Using knuckles, gently pull dough outward from center until desired consistency is reached. Be sure to leave an outer edge for crust.
Ladle panna onto pizza, spreading evenly over the surface and making sure to leave pronounced crust. Season with cracked black pepper to taste. Spread mushrooms and onions evenly on top of panna, making sure everything is evenly distributed to prevent pizza from tearing in oven. Top with grated provolone.
Transfer to oven and bake for 7–10 minutes, or until crust is browned on bottom and cheese
is melted. Remove from oven and grate Grana Padano over pizza to finish.
Place ricotta in medium bowl and use whisk to whip.
Slowly add heavy cream until it takes on a silky consistency.