While asparagus simmers, whisk 3 eggs in a large bowl.
Once asparagus cream mixture is tender, blend it in a high-powered blender, then pass the puree through a strainer.
Slowly add the strained asparagus puree to the large bowl of eggs, whisking constantly. Season to taste.
Spray 4 oz ramekins with non-stick spray and pour 3 oz asparagus cream into each ramekin, filling ramekins about 3/4 full.
Place ramekins in a large roasting pan, pour in boiling water until water level is halfway up ramekins. Cover with foil and bake for 20 - 30 minutes, until custard is fully set (checking every couple of minutes after 20 minutes in the oven).
When custard is set, refrigerate them until cold, then remove them from their ramekins and place them on each plate.