Homemade Salisbury Steak

For the steaks:

• 1 lb. (450g) ground lean beef
• 1 green pepper, finely chopped
• ¼ cup (30g) bread crumbs
• 1 egg
• 2 tsp. tomato ketchup
• 1 tsp. dijon mustard
• ½ tsp. dried parsley
• ½ tsp. onion powder
• ¼ tsp. salt
• 1 tsp. olive oil

For the gravy:

• 2 tbsp.butter
• 2 tbsp. all purpose flour
• 1½ cups (350ml) beef broth
• 1 tsp. tomato ketchup
• 1 tsp. Worcestershire sauce
• ½ tsp. onion powder
• 3 cups (250g) brown button mushrooms, sliced