Soak gelatin. Mix the crème fraîche, sour cream, sugar to taste and lemon juice. Dissolve the gelatine over a mild heat and add a few tablespoons of the sour cream while stirring constantly. Then stir the gelatine into the cream and cool it until it has set a little. Whip the cream, fold into the cream and pour into a glass bowl. Puree the strawberries, sweeten with a little sugar and pour over the cream.
If you like, you can also prepare this dessert with raspberries. These then have to be mashed and passed through a fine sieve.