Dump in 8 ounces of shortbread into a bowl of a food processor.
Pulse until the cookies are slightly broken down.
Add the 8 tablespoons of unsalted butter and 1/3 cup sugar to the processor.
Pulse again until mixed and smooth.
In a greased 8x8 pan scoop the shortbread mixture out of the processor and spread an even layer at the bottom of the pan.
Spread the full jar of lemon curd over the the cookie mixture.
Top with shifted powdered sugar and 1 tablespoon lemon zest.
For the ice cream:
In a small bowl whisk together the sugar, milk, vanilla, and malted milk.
Mix until the sugar has dissolved and the malted milk is mixed in.
Add the whipping cream and mix slowly for 1 minute.
Poor the milk mixture into an ice cream machine.
Turn the machine on and churn for 20 minutes.
Turn the machine off and add 3 ounces or 8 cookies that have been smashed to the ice cream machine.
Churn for an additional 2-5 minutes until the cookies are incorporated.
Once done turn the machine off and spoon the ice cream into a freezer safe container in batches, in between each spoonful add a spoonful of marshmallow cream until the jar has been added to all of the ice cream.
Place in the freezer for 2 hours.
In the bottom of a bowl add one lemon bar square topped with one scoop of ice cream.