Melt the butter in a pan and let it fizz without browning. Add the flour and stir until golden yellow. Let go a few minutes until shiny. Pour the stock little by little to the mixture until it is completely mixed and shiny. Let is go for a few minutes until it is done.
Add the gelatine and then the cream, eggs, worcestershire sauce and mustard. Bring to the taste with salt, pepper and nutmeg. Mix with the cheese and a last the parsely. Cool the ragout in a flat bowl overnight, covered with cling film.