Pre-heat the oven to 180ºC.
Spray the chips with low calorie cooking spray and toss them in the onion salt.
Scatter on a baking sheet and cook in the oven for 40-45 minutes, turning halfway through until the centre of the chips are soft and they're crisp and golden on the outside.
Meanwhile, make the gravy. Put all of the ingredients except the gravy browning in a saucepan, add 600ml of water and bring to a boil.
Reduce the heat and simmer for 25 minutes.
When the carrots and potatoes are soft, blitz with a hand blender. Add a couple of drops of gravy browning if required. If the gravy is too thick then add a little water until it reaches a consistency you are happy with. Keep hot until the chips are cooked.
Mix the grated cheddar and mozzarella together.
When the chips are cooked, divide between 2 warmed bowls. Sprinkle half the cheese mix over, smother with the hot gravy, then sprinkle over the rest of the cheese. The heat from the gravy will melt the cheese.
Serve and enjoy!