This is an excellent go to quick dessert idea- although we serve them as canapés. A large one with tons of mixed berries would look excellent.
You can also use a pre made tart shell to be truly expedient.
Mix custard and cream together, adding some sugar or vanilla extract if you like it especially sweet- essentially a cheat’s crème pâtissière. Spoon a blob into a tart shell, adding the berries on top. Edible flowers add a certain panache but are not massively essential.