Gourmet Beef and Guinness Pies with Flaky Puff Pastry & Creamy Mash

Ingredients

• 2 pounds boneless beef chuck, cut into 1-inch cubes
• 2 tablespoons olive oil, divided
• 1 1/2 cups yellow onion, chopped (about 1 large)
• 1 cup carrots, diced
• 1 cup celery, diced
• 4 cloves garlic, minced
• 2 tablespoons tomato paste
• 1 teaspoon dried thyme
• 1 bay leaf
• 1 1/2 cups Guinness stout (or other dark beer)
• 2 cups beef broth
• 1 teaspoon coarse sea salt
• 1/2 teaspoon freshly ground black pepper
• 4 cups all-purpose flour, divided
• 2 1/4 sticks (18 tablespoons) unsalted butter, very cold, divided
• 1 cup ice water
• 1 egg, lightly beaten, for egg wash
• 3 pounds starchy potatoes (e.g., Russet or Idaho), peeled and quartered
• 1/2 cup heavy cream, warmed
• 1/4 cup unsalted butter, softened
• 1 pound frozen green peas