Tart Crust:  In a food processor, combine flour, powdered sugar, and salt.  Add cold butter pieces and pulse until sandy.  Add egg yolk and 1 tablespoon of cold water.  Continue to pulse until dough just comes together (add more water only if needed). From into a log, about 2-1/2 inches in diameter.  Or, you can do using a pastry blender tool.

Wrap in saran wrap and chill for 20 minutes.  If refrigerated longer, let stand for about 30-45 minutes so the dough isn’t rock hard. 

Slice off discs and either press dough, or roll out and cut circles, into tart molds. Pierce bottoms with a fork.  Remember to save a little dough for the snowflakes.

Bake at 350 degrees for 15 minutes, or until lightly golden. Let cool completely.

Lemon Custard:  Heat milk and cream in a saucepan until warm.

In a large bowl, whisk egg yolks, white sugar, cornstarch and lemon zest.  Slowly pour warm milk mixture into yolk mixture while whisking.  Return to saucepan and cook on low heat, stirring constantly, until thick.  Remove from heat and add lemon juice and butter.  Mix until glossy and smooth.   Transfer to a bowl, cover with saran wrap directly touching the custard.  Cool then spoon into tart shells.  Or refrigerate until ready to assemble. 

Snowflake Cookie Toppers:  Roll leftover shortbread dough ¼ inch thick. Cut snowflake shapes using a cookie cutter. Bake at 350 degrees 8–10 minutes, until lightly golden on the edges.  Cool and dust generously with powdered sugar.

Assemble Tarts:  Spoon chilled lemon custard into baked tart shells.  Place one snowflake cookie gently on top of each tart. Dust again with powdered sugar for a snowy finish.

Serve cold or room temperature.   

Makes 8 mini tarts