Peel and finely dice the onion and garlic. Peel and slice the ginger. Wash the lemon grass, dab dry and pound a little. Heat 2 tablespoons of oil in a saucepan.
Sauté the garlic, lemongrass, ginger and onions for 1-2 minutes. Stir in curry paste and steam briefly. Meanwhile cut open the vanilla pod and scrape out the pulp. Wash the lime hot, grate dry and grate the peel.
Halve the lime and squeeze it. Add the pod, marrow, caraway seeds, lime zest and tomatoes to the pot. Cover and simmer for 6-7 minutes. In the meantime heat 2-3 tablespoons of oil in a pan. Fry the sausages in the pan for about 6 minutes until golden brown.
Remove the vanilla pod and lemongrass from the pot. Season the sauce with lime juice, honey, pepper and a little salt. Remove the sausages, drain them on kitchen paper, cut them into pieces, arrange them on plates with crab chips and pour the sauce over them.