Brown Sauce

Ingredients (9)

• 1/2 cup unsalted butter
• 1 celery rib
• 1/2 medium yellow onion
• 1 carrot
• Few sprigs of fresh thyme
• 6 cups beef stock
• 2 tbsp Worcestershire sauce
• 1/2 cup all-purpose flour
• Kosher salt and freshly ground black pepper