Rinse the poppy seeds under cold water in a fine mesh colander; transfer to a medium saucepan with three cups of cold water. Bring to a simmer over medium heat (do not boil). Remove from the heat and let sit in the saucepan, covered, for 30 minutes at room temperature. Repeat – return the mixture to a simmer, remove from the heat and let sit for another 30 minutes at room temperature, covered.

Drain poppy seeds thoroughly, using a fine mesh colander or couple layers of cheesecloth. Squeezing as much of the water as possible.

Place the poppy seeds in a food grinder (either coffee grinder or food processor – with grinder option turned on) and grind.

Mix in eight to 10 ounces (I used about 10 ounces) sweetened condensed milk into the ground poppy seeds and mix well; refrigerate until ready to use.

In a large bowl, beat cream cheese, butter, and granulated sugar with a hand held mixer on medium speed. Beat in lemon zest, vanilla, and salt. Gradually beat in flour on low speed until combined.

Divide the dough into four portions and wrap each portion in plastic wrap. Chill in the refrigerator for one hour.

On a lightly floured surface, roll one portion of the dough at a time into a nine-inch circle. Spread one-quarter cup of the poppyseed filling over the circle, leaving a half-inch uncovered edge.

With a sharp knife, cut circle into 12 wedges. Starting at the wide end of each wedge, roll up toward the center. Place each pastry on a parchment-lined baking sheet one inch apart; cover and refrigerate for 45 minutes.

Preheat the oven to 350 degrees Fahrenheit.

In a small bowl, whisk the egg with milk. Brush each pastry with egg wash. Bake for 15–20 minutes or until lightly golden. Transfer to a wire rack to cool.

Sift powdered sugar over the pastries and serve.