Kielbasa & Pretzel Overnight Breakfast Bake - Chew Nibble Nosh

Ingredients

• 1 lb. pretzel bread, cubed
• 1 (14.5 oz.) package kielbasa, halved lengthwise, and sliced
• 1 Tbsp. canola oil
• 3 cups thinly sliced onions
• 3 cloves garlic, minced
• 10 eggs
• 1 1/2 cups heavy cream
• 1/2 cup low-sodium beef broth
• 1/2 cup spicy brown mustard
• 2 Tbsp. chopped fresh chives
• 1 tsp. chopped fresh Thyme
• 2 tsp. kosher salt
• 1 tsp. black pepper
• 8 oz. Gruyère cheese, shredded, divided