Briefly blitz the digestive biscuits in a food processor to create crumbs, or alternatively place them in a plastic bag and crush them with a rolling pin.
Melt 3 tbsp of butter and mix this into the crumbs. Divide the mixture into the jars, pressing down slightly. Set aside.
To make lemon curd, melt 1/2 a cup of butter with sugar, lemon juice and the zest in a double boiler. Whisk the eggs together in a separate bowl.
Once the butter, sugar and lemon mixture has melted, slowly whisk in the eggs one at a time. Keep the mixture in the double boiler for about 10 minutes, continuously stirring with the whisk until it thickens. Transfer the mixture to a piping bag and refrigerate.
In a bowl, whisk the cream cheese, icing sugar, and vanilla essence together. Transfer the mixture to a piping bag.
Pipe the cream cheese mixture into the jars and follow with the lemon curd mixture. Refrigerate until ready to serve.