French Onion Rice Pilaf

Ingredients

• 2 yellow onions, thinly sliced ~⅛ inch thick.
• 4 tbsp. Butter
• pinch of salt
• 8 tbsp. unsalted Butter, divided
• 4 cloves garlic, pressed thru a garlic press
• 2 cups basmati rice
• 4 cups Beef broth
• 1 tbsp. Fresh Thyme, plus more for garnish
• salt and pepper to taste
• 1 cup Gruyere, shredded
• 1 cup mozzarella, shredded