Stir the sour cream with the spices until smooth.
Stir in the gelatine.
Carefully fold in the cream and the snow.
Cut off the tomato cap and scoop out with a small spoon – fill with the sour cream mousse, put the cap back on.
Allow to set in the refrigerator for about 1 hour.
Arrange on a plate and garnish with basil, rue and cocktail tomatoes.