For the bechamel sauce, melt the butter in a saucepan and mix in the flour. Take the pot off the stove for a moment and stir in the milk. Add the stock cube and bring to the boil while stirring.
Fry the minced meat in oil and add the tomato pieces. Season with salt, pepper, mustard and garlic. To taste.
Put a layer of minced meat in a greased casserole dish, then add about 1/3 of the béchamel sauce, then add the lasagne plates. Repeat this until it makes 3 layers. Finish with the minced meat and bechamel sauce. Sprinkle with cheese.