Loaded Greens with Walnuts and Mushrooms

Ingredients

• 3 Tbsp. extra virgin olive oil, plus more if needed
• 1 small yellow onion, thinly sliced
• 3 cups thinly sliced cremini mushrooms, tough stems removed
• Kosher salt and freshly ground black pepper
• 1 cup walnut halves, roughly chopped
• 2 pounds collard greens, stems removed and leaves roughly chopped
• 1 tsp. ground turmeric
• 2 Tbsp. red wine vinegar