Caramelized Onion and Mushroom Pie

Ingredients

• 3 tbsp extra-virgin olive oil (divided)
• 6 cups onions (halved and sliced to desire thickness)
• 1 1/4 tsp kosher salt (divided)
• black pepper (to taste)
• 2 tbsp unsalted butter
• 1 rosemary sprig and 1 sage sprig (tied together)
• 4 cups diced mushrooms
• 1/2 cup dry marsala
• 2 tsp red wine vinegar
• 1/4 cup panko breadcrumbs
• 1 cup grated gruyere cheese
• 1 uncooked pie crust
• chopped arugula (for topping)