Heat roughly 2 tablespoons of oil in a pot over medium heat. Add the diced onion and chopped garlic, cooking for 2-3 minutes until softened. Grate the carrots and add them to the pot with 250 ml water and the vegetable stock cube. Add the leek. Bring to a boil, then simmer for 5-8 minutes until the carrots are tender but still slightly firm. Season lightly with salt and pepper.
Pour 500 ml of water into the pot, add the millet and bay leaf. Bring to a boil, then reduce heat to medium-low and simmer for 15-20 minutes until the millet is cooked through. Remove from heat and stir in the oat flakes, diced cheese, and fried onions. Season to taste with salt and pepper. Add a pinch of curry powder and a pinch of ginger powder (or fresh ginger, to taste, if preferred). Let rest for 15 minutes.
Transfer the mixture to a bowl and cool to room temperature. Mix in the egg, flour, and quark until well combined. Using a tablespoon, form the mixture into patties. Heat oil in a pan over medium-high heat until shimmering. Fry the patties in batches if needed, for 3-4 minutes per side until golden brown. Ensure the patties develop a deep golden crust, as patties that are too light may fall apart.
Serve warm as a side dish or main course. The patties also taste good served cold. Optional variants: stir canned peas or canned corn into the mixture before forming patties; or heat a little oil in a pan over low heat, add paprika and cook for 1 minute until fragrant, then stir into the mixture before forming patties.