Stale bread is key: leave bread slices out for an hour before assembling, or dry them in a 250°F oven for 5 minutes. Do not skip draining the strawberries—the liquid will make the cream runny. Chill the assembled sandwiches for at least 30 minutes before slicing for clean edges. The cream base (without berries) can be made up to 3 days ahead. Macerated berries can sit in sugar for up to 24 hours in the fridge; drain before folding in.