Preheat oven to 300 degrees F

Place butter, sugar, salt into your stand mixer or a large bowl, and mix for five minutes or until sugar, salt are well incorporated, and your butter has taken on a deeper yellow color, that’s a good indicator that your ingredients are creamed.

Add in your vanilla and flour and stir well, eventually using your hands to create a dough.

Press the dough into your the parchment paper-lined tart pans. Press holes with a fork into your dough and bake in the preheated oven for 25 minutes. Check that your cookie is golden brown. It will harden more once removed from oven. Let it cool before adding your lemon curd.

In a mortar and pestal or food processor, make a lemon basil sugar by adding your rosemary, lemon zest and sugar. Finely process until it's a very fine sugar.

Pour mixture into a double boiler or your homemade double boiler and mix your lemon zest, lemon juice, fresh basil sugar, and eggs until well combined.

Place double boiler bowl over simmering (not boiling) water in a medium-size pan.

Once your water is simmering, reduce heat. You do not want to overcook your eggs.

Stir continuously to ensure eggs are not overheating.

Continue stirring consistently for 10 minutes, finally adding your butter and mixing until completely incorporated. I do not multi task while making lemon curd. At this point, your lemon curd should be nice and thick. If not, continue cooking and mixing constantly. It will continue to thicken further as it cools over your cookie crust.

When your curd is nice and thick pour the curd over your baked and cooled shortbread tarts and let it cool in your fridge for at least two hours before serving.