Peel and finely chop the onion. Grate cheese
Cook the pasta in plenty of boiling salted water for about 12 minutes
Heat the fat. Sauté the onion in it. Add flour and sauté. Add 1/4 l water and milk while stirring. Stir in stock, bring to the boil and simmer for about 5 minutes. Melt both cheeses in it while stirring. Season to taste with salt and pepper
Clean, wash, quarter, seed and dice the tomatoes. Arrange drained pasta with sauce and the ham. Sprinkle with tomatoes and garnish with basil as desired
Drink: juice spritzer