For Poppy Seed Filling:

In a medium saucepan, combine poppy seeds, whole milk and honey.  Let sit for 1 hour at room temperature.*  Prepare Shortbread Crust during this time (see below).

After 1 hour, add heavy cream and lemon zest to poppy seed mixture.  Over medium-low heat, stirring frequently, cook the poppy seed mixture until the mixture thickens, about 15-20 minutes.  The milk should be reduced by about half.

Whisk cornstarch and orange liqueur in a small bowl.  Once poppy seed mixture reaches a gentle boil, add the cornstarch mixture to it. Stir continuously to avoid clumps, about 1-2 minutes.  Mixture will continue to thicken.

Remove saucepan from heat and stir in ground walnuts and unsalted butter.  Stir until unsalted butter has melted completely and mixture is warm.  Stir the slightly beaten egg in until well combined.  It’s important the poppy seed mixture is warm when you add the egg, otherwise the egg may cook and cause a chunky filling.

Pour warm poppy seed filling over the top of the warm shortbread crust.  Return pan to the oven.  Bake for 15-17 minute more or until filling has puffed slightly and is set.  The edges should be golden brown. Cool pan on a wire rack. Dust with powdered sugar, cut into 2-1/2 inch squares, and serve.

For the Shortbread Crust:

Cream unsalted butter, powdered sugar and salt together.  Add vanilla and mix well.  Blend in all-purpose flour until well combined.

Press dough evenly into a lightly greased 9″X13″ baking pan. Place pan into refrigerator to chill for about 30 minutes.

Preheat oven to 350 degrees F.  Remove pan from refrigerator.  Bake crust for 20 minutes or until lightly golden brown and set.  Remove from oven and cool slightly.