¼ cup olive oil
1 ¼ lb. beef chuck, cut into 1" cubes
3 cloves garlic, finely chopped
2 large yellow onions, sliced
2 ribs celery, thickly sliced
2 small carrots, thickly sliced
2 tbsp. minced rosemary
1 12-oz. bottle stout beer
¼ cup flour
2 cups beef stock
2 tsp. mustard powder
1 bay leaf
1 tbsp. unsalted butter
10 oz. mushrooms, quartered
6 oz. English Stilton, crumbled
1 10-oz. package frozen peas
1 14-oz. package puff pastry
1 egg, lightly beaten