Put the morels in a bowl, cover with 300ml boiling water and set aside to soak for 30 minutes.
Meanwhile, blanch the asparagus in boiling salted water for 1 -2 minutes until almost cooked.
Plunge into iced water to refresh, then drain. Set aside.
Drain the morels, reserving the soaking liquid, and rinse under cold water.
Squeeze out excess liquid, then coarsely chop and set aside.
In a small pan, heat 2 tbsp of the olive oil and sauté the morels and button mushrooms for 5 minutes.
Add the splash of sherry and let it bubble up.
Reduce the heat, add the cheese sauce and enough of the reserved morel soaking liquid to make a thin but creamy sauce.
Simmer for a minute or so, stirring. Set aside.
Heat the remaining olive oil in a frying pan and quickly stir-fry the asparagus to warm through.
Tip out onto a serving plate, then spoon over the cheesy morel sauce.