First wash the strawberries and then hull and pat dry.
In a large mixing bowl, whip the egg yolks and sugar together until the mixture has thickened.
Now pour the cream into a small pan and bring to the boil.
Using an electric whisk, slowly pour the cream over the egg mixture, whisking continuously.
Return the mixture to a clean pan and let it cook over a low heat, beating with a wooden spoon, until the mixture has thickened and will coat the back of the spoon. (The heat needs to be low because the custard must not be allowed to boil or it will curdle.) Then leave to cool.
Meanwhile, purée half the strawberries in a food processor or blender, and then pour into a bowl.
Reserve four whole strawberries for decoration from the other half. Dice the remainder.
Add the diced strawberries to the purée and then add the cooled custard and gently stir together.
Fold in the crème fraîche and a couple of drops of lemon juice until well incorporated.
Spoon equally into the four dishes and chill for at least four hours.
Garnish the top with a reserved strawberry before serving.