Beef & Guinness Pie - Dinner With Julie

Ingredients

• canola or olive oil, for cooking
• 1 large purple onion, chopped
• 2 carrots, peeled and chopped
• 2 celery stalks, chopped
• 2 cups quartered mushrooms
• 4-5 garlic cloves, chopped or crushed
• 2 lbs. beef brisket or stewing beef, cut into 1-inchcubes
• salt and pepper
• 2 Tbsp. flour
• 1 can or bottle of Guinness
• chicken or beef stock or water
• 1 cup grated old cheddar (optional)
• 1 pkg. frozen puff pastry, thawed (or half a batch of rough puff)
• 1 egg, lightly beaten with a fork, for brushing on top (optional)