First cook the lentils in boiling water for 15-20 minutes or until tender, but still with a bite. Drain in a colander.
While the lentils are cooking, brush the sausages with a little sunflower oil and place them on the BBQ, turning every 5 mins or so – not too hot!
Warm the olive oil in a saucepan and sweat the onion, garlic and ginger until soft. Add the curry paste and some seasoning and cook for 2-3 minutes. Stir in the lentils, add the stock and bring to the boil. Add the tomatoes and 2 tablespoons of chopped coriander or chervil.
Check the seasoning. Simmer for 30 seconds, or until you have a loose sauce; not too wet, not too dry. Remove from the heat and stir in the crème fraîche. This can be done ahead and gently reheated.
When your sausages are golden brown all over and cooked through, divide the lentils between 4 warmed serving bowls, making sure the sauce is evenly distributed. Set the sausages on top, garnish with the rest of the chopped coriander and serve.