Those who are particularly diet-conscious could dispense with this step, and with the cream. A caution regarding seasoning. Potatoes absorb a lot of salt so you may find it undersalted. The caviar on the other hand, is very salty. This, for me, is a delightful and important contrast.
Guests can always add extra salt if they choose.
Water biscuits are made by Carr's, amongst others, and can be found in most supermarkets, possibly in the gourmet food section. They are variously known as water biscuits, water crackers and table water crackers. To my mind the best for eating with cheese are the high-bake ones, but the regular type are better for this recipe. If you can't find them, then any round dry bland low-salt cracker will do. I suppose if budget is a prime consideration one could dispense with the caviar, too, but that would be like serving a martini without the olives.