Shepherd's Pie with Guinness: My Irish Comfort Food!

Ingredients

• 2 lbs (900g) boneless lamb shoulder, cut into 1-inch cubes
• 1 tbsp olive oil
• 1 large onion, chopped
• 2 carrots, peeled and chopped
• 2 celery stalks, chopped
• 2 cloves garlic, minced
• 1 tbsp tomato paste
• 1 tbsp all-purpose flour (15ml)
• 1 bottle (11.2 oz / 330ml) Guinness stout
• 2 cups (475ml) beef broth (low sodium)
• 1 tbsp Worcestershire sauce (15ml)
• 1 tsp dried thyme (5ml)
• 1 bay leaf
• Salt and freshly ground black pepper to taste
• 1 cup (120g) frozen peas, thawed
• 3 lbs (1.36kg) Yukon Gold potatoes, peeled and quartered
• 1/2 cup (120ml) whole milk
• 4 tbsp (57g) unsalted butter
• 1/2 head green cabbage, finely shredded
• Pinch of ground nutmeg