Beef and blue cheese sliders

Ingredients

• 1 tablespoon olive oil
• 1 small onion, very finely chopped
• 500 grams beef mince
• 2 tablespoons chopped parsley
• 1 tablespoon Worcestershire sauce
• 1 teaspoon Dijon mustard
• salt and pepper
• 1 tablespoon oil, extra
• 80 grams blue cheese, cut into 10 slices
• 10 slider buns
• 10 baby lettuce leaves
• 2 large tomatoes, sliced
• selection of sliced onion, tomato relish, cornichons, to serve