Mix the yolks with the sugar until creamy, then add the starch and warm milk and continue mixing. Put the mixture in a saucepan and put on medium heat, stirring continuously for 5-7 minutes until the composition thickens a little. Leave to cool. When it has cooled, add the lemon juice and finely grated peel and mix in one part until incorporated. Whip the cream and incorporate it into the cold egg cream.
Put the bowl / casserole in the freezer and take it out every hour, 3 times, and mix with a spoon.