Heat the oil and butter in a heavy saucepan and cook the onion for 10 minutes until soft.
Add the rice and stir to coat the rice in the butter.
Add the wine and stir well cooking until the volume reduces by half.
Start adding the stock a ladleful at a time, stirring, over medium heat.
Add more stock to keep the rice wet and allow it to slowly absorb the liquid. Cut off the woody ends of the asparagus and finely chop all of them.
Cook the chopped asparagus in simmering water until tender.
Drain and cool under cold running water.
When the rice is just cooked, add the drained chopped asparagus, nutmeg, salt and pepper and fold through.
Beat in the butter and cheese, cover and rest off the heat.
Heat the remaining olive oil and sear the scallops for 3 minutes on one side and briefly on the other.
Divide the risotto between four warm dinner plates and arrange the scallops, scatter with sea salt, pepper and grated lemon rind.