Rinse, hull and puree the strawberries. Strain through a sieve and mix with the lemon juice.
Beat the egg yolks, sugar, cardamom and vanilla sugar over a hot water bath until creamy (do not over heat). Then remove from the heat, beat until cool and stir in strawberry puree. Beat the cream until stiff and fold into the mixture. Finish in an ice cream maker or freeze in a shallow container in the freezer, stirring occasionally.
Serve scooped into bowls, garnished with strawberries if desired.