Combine the egg yolks, sugar, and lemon juice in a medium saucepan and cook over medium heat.
Whisk until the mixture thickens, about 8 minutes.
Stir in the butter, 1 piece at a time.
Continue cooking until the mixture is thick enough to coat the back of the spoon.
About 5-7 minutes,
Pour mixture into a bowl but by using a fine-mesh sieve. This helps to collect any pulp.
Stir in the lemon zest and salt and let cool completely.
For the Bars
Spray an 8x8 inch baking dish with cooking spray and then line with aluminum foil.
Combine graham crackers in a food processor and pulse until they are finely crumbled.
Add the melted butter and lemon zest and pulse again until all combined.
Transfer to the baking dish and pack tightly into the pan.
Spread ice cream over crumb mixture and place back in freezer for just a few minutes to help it firm up, but not completely. Only if the lemon curd has cooled then pour over the ice cream. If it's not cooled then keep the ice cream in the freezer and it's fine if it freezes again.
Once the lemon curd has been poured over the ice cream then place back in the freezer for at least four hours.
Before serving cut into squares and dust with powdered sugar.
Vanilla or blueberry ice cream would be great in place of the strawberry. Also, if you don't want to use the lemon curd then just omit it from the steps listed above.