1 In a hob, pop in all the ingredients above that say “for the sauce” and heat until smooth. Leave to the side and butter your bread and then your grill on.
2 In a frying pan, fry your mushrooms and tarragon for around 5 minutes on a gentle heat and then add in 3/4 of the cheese sauce to your mushroom mix.
3 Grill your bread for 3 minutes and then pour your mushroom sauce on two of the slices.
4 Sandwich them with the other slices and cover with remaining sauce and grill for two minutes whilst you fry your duck eggs in the same pan as your mushrooms. Then enjoy!