One-Pan French Onion Mac & Cheese

Ingredients

- 6 servings +

• 3 yellow onions, thinly sliced
• 3 tbsp butter
• 1 tbsp olive oil
• 1 tsp sugar, optional, speeds caramelisation
• 1 tbsp balsamic vinegar
• 1 lb elbow macaroni
• 3 cups beef broth, low sodium
• 1 cup whole milk
• 1 cup heavy cream
• 2 cups Gruyère cheese, shredded
• 1 cup sharp cheddar cheese, shredded
• 1 tsp Dijon mustard
• 1 tsp fresh thyme, leaves
• 1 tsp kosher salt, or to taste
• ½ tsp black pepper