In a large skillet, heat a drizzle of oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until they become translucent and fragrant.

Increase the heat to medium-high and add the ground beef to the skillet. Cook for 4-5 minutes until browned.

Stir in the minced garlic, curry ketchup, mustard, tomato paste, and brown sugar into the skillet. Combine well and let simmer for 2-3 minutes.

Season the mixture generously with salt and pepper to taste. Allow the filling to cook for another minute or two.

Butter one side of each slice of sandwich bread, then toast the slices in a skillet for about 2-3 minutes per side.

On half of the toasted slices, spoon the beef mixture and sprinkle shredded cheddar cheese over the top.

Return the sandwiches to the skillet and grill them for another 2-3 minutes on each side.

Once golden, remove from heat, cut in half and serve immediately.