This is a particularly quick and easy summer dessert, especially if you make the bases three to four days ahead and then fill and top them at the last moment.
To make the bases, mix all the ingredients together and press one-quarter into an 8 cm (3¼ in) pastry cutter, bringing it up around the edge inside the cutter to form a concave centre. Chill briefly until the base comes out of the cutter easily, then make three more in the same way.
To make the filling, whip all the ingredients together until semi-whipped but stil