French Onion Penne

Ingredients

• 2 tbsp. butter
• 1 large onion, thinly sliced
• kosher salt
• Freshly ground black pepper
• 2 cloves garlic, minced
• 1 tbsp. fresh thyme leaves, plus more for garnish
• 1 packet French onion soup mix (such as Lipton's)
• 1 lb. penne pasta
• 2 c. beef broth
• 2 c. water
• 1/4 c. heavy cream
• 1 1/2 c. shredded Gruyere