Have the toast buttered and on a hot dish.
Put the butter in a small sauce-pan, and when hot, add the dry flour. Stir until smooth, but not brown; then add cream, and let it boil up once.
Put the oysters (in their own liquor) into a hot oven, for three minutes; then add them to the cream. Season, and pour over the toast. Garnish the dish with thin slices of lemon, and serve very hot.
It is nice for lunch or tea.