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.