Start your custard by combining the sugar, cornflour, lemon zest and 1/2 cup of milk in a medium saucepan. Whisk to combine.

Add in the remaining milk and heat on a medium heat until the mixture is warmed through. Stir occasionally.

While the milk is heating, prepare your eggs. In a small bowl, combine the eggs and cream. Whisk well to break up the eggs.

Once the milk is warm, pour the egg mixture into milk mixture in a slow, steady stream. Mix slowly until combined.

Continue to heat, reducing the temperature to low. Stir constantly until the mixture has thickened. This should take about 10 minutes.

Remove your saucepan from heat and stir through the sour cream and lemon juice.

Use a strainer over a medium sized bowl to strain the custard and remove the lemon zest if desired.

To serve warm, use immediately or else you chill the custard to serve later.