Step 1
Preheat oven to 220C/200C fan forced. Heat the oil in a large, deep frying pan over medium-high heat. Add the beef, onion and garlic. Cook, using a wooden spoon to break up any lumps, for 10 minutes or until browned.
Step 2
Combine the gravy powder and 250ml (1 cup) water in a bowl. Add tomato sauce, Worcestershire and mustard to the pan. Stir until combined. Pour in the gravy mixture and bring to the boil. Cook for 1 minute or until the mixture thickens. Transfer mixture to a 1.5L (6 cup) baking dish. Top with the cheese slices then scatter over the cheddar.
Step 3
Arrange chips on top. Sprinkle with sesame seeds. Roast for 35 minutes or until chips are golden and cooked through. Top with pickles.