Prepare all ingredients and make sure the air fryer basket is clean and dry. Preheat the air fryer to 200°C if recommended by the manufacturer. Place the frozen French fries in a bowl. For stronger browning, optionally toss them with one tablespoon of rapeseed oil. Spread the fries loosely and as evenly as possible in the basket. Do not overcrowd it so the hot air can circulate properly. Cook the fries at 200°C for an initial 10 minutes.

Meanwhile, peel the onion and garlic clove. Finely dice the onion and finely chop the garlic or press it through a garlic press. Cut the sausages diagonally into slices about two centimeters thick. Alternatively, cook them whole and slice them afterward.

Melt the butter in a small saucepan over medium heat. Add the diced onion to the melted butter and sauté, stirring occasionally, until translucent. Add the garlic and cook for about 30 seconds without allowing it to brown.

Add the curry ketchup, tomato ketchup and mayonnaise to the saucepan. Add the curry powder, paprika, chili flakes and a small pinch of salt. Stir the sauce thoroughly and gently simmer it over low to medium heat for about five minutes. Stir the curry sauce occasionally to prevent it from sticking to the bottom of the pan.

After the first 10 minutes, pull out the basket and shake the fries thoroughly or turn them with tongs. Add the sausage slices to the fries and arrange them so they are not completely stacked on top of one another. Cook the fries and sausage for another 8 to 10 minutes at 200°C. Shake the basket again halfway through the remaining cooking time so the fries and sausage brown evenly. Check that the fries are crisp and the sausage is fully heated and golden brown. Extend the cooking time by two to three minutes if needed.

Taste the sauce and adjust with additional curry powder, salt or chili flakes as desired. Divide the cooked sausage pieces between plates or serving bowls. Spoon the warm curry sauce generously over the sausage and sprinkle with additional curry powder. Arrange the crispy fries alongside, season them with salt to taste and serve the dish immediately while hot.