2 pounds chuck steak, cut into 1 1/2-inch cubes
1/2 cup all-purpose flour
2 tablespoons olive oil
3 celery stalks, diced
1 onion, diced
3 carrots, sliced
8 ounces button or cremini mushrooms, sliced
2 bay leaves
1 1/2 cups frozen peas
1 1/2 cups beef broth
2 teaspoons kosher salt
1 teaspoon freshly ground black pepper
1/4 cup tomato paste
1 sheet frozen puff pastry, thawed
Season the beef with salt and pepper and dredge in the flour. Heat the oil in a large skillet over medium-high heat until it shimmers. Add the beef and cook, stirring frequently, until browned on all sides, about 5 minutes.
Transfer the beef to the slow cooker and add the onion, celery, carrot, mushrooms peas, broth, salt, pepper, tomato paste and bay leaves. Cover and cook on high for 6 hours.
Preheat the oven to 400 F and line a baking sheet with parchment paper.
Roll the puff pastry out to 1/4-inch thickness. Cut into 3-inch squares and arrange them on the baking sheet in a single layer. Bake for about 15 minutes, until golden brown.
Serve the stew topped with the pastry squares.