Wild Mushroom Stuffed Burger with Red Onion Slaw and Herbed Mushroom Fondue - Sutter Home Family Vin

Ingredients

• 10 large Portobello mushrooms, stems removed (leave the dark gills on the mushrooms), cleaned
• 3 Tbsp. avocado or grapeseed oil, divided
• 3/4 tsp. fine sea salt
• 1 1/2 tsp. freshly ground black pepper
• 2 Tbsp. minced fresh sage
• 1 Tbsp. balsamic vinegar reduction or "glaze"
• 4 oz. chopped applewood smoked bacon
• 1 cup finely chopped grilled mushrooms (from step #2 below)
• 2 Tbsp. porcini mushroom powder (you can get this at a specialty store or grind your own)
• 1 1/2 tsp. fine sea salt
• 2 tsp. freshly ground black pepper
• 3 Tbsp. minced fresh sage
• 1 3/4 lbs. ground chuck (80% lean, 20% fat)
• 3 large red onions, peeled (leave attached at the root end) and quartered
• 1 cup Dijonase mustard
• 1/4 cup Dijon mustard (Grey Poupon)
• 1 tsp. fine sea salt
• 1 tsp. freshly ground black pepper
• 1 1/2 cup freshly grated gruyere cheese
• 2 Tbsp. cornstarch
• 1 1/2 cups heavy cream (the highest butterfat cream you can get- preferable unpasteurized)
• 1 1/2 cups sliced grilled mushrooms (from step #2 below)
• 1 Tbsp. minced fresh sage
• avocado or grapeseed oil for oiling grill, burgers and buns
• 6 prepared uncooked burgers (from step #3)
• 6 onion challa or brioche hamburger sized (about 4 1/2"-5" in diameter) rolls