Preparation

Make the dough

• In the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl using a hand-held electric mixer), cream the cream cheese, butter, and sugar on medium speed until light and fluffy, 2 minutes. Add the flour and salt, and then mix just until a smooth dough forms. Divide into 4 equal disks if making crescent shapes or 4 equal squares if making pillow shapes. Wrap in plastic and chill for 1 hour or up to overnight.

Make the filling

• In a small saucepan, combine the sugar, zest, lemon juice, butter, and egg, and cook over medium heat, whisking continuously until thickened, about 5 minutes. Stir in the poppyseeds. Let cool completely, then chill for at least 1 hour.

Fill, shape and bake the rugelach

• Position a rack in the center of the oven, and heat the oven to 375°F. Line 2 large rimmed baking sheets with silicone baking mats or parchment lightly coated with cooking spray.
• To shape crescents, remove one dough disk from the refrigerator, and place on a lightly floured work surface. Roll into a 9-inch circle. Spread one-fourth of the filling on the dough, leaving a 1/2-inch edge, and then slice into 12 wedges. Roll each wedge into a crescent shape from the outside edge in.
• Alternatively, to make pillow shapes, remove one dough square from the refrigerator, and place on a lightly floured work surface. Roll the dough into an 8-inch square. Spread one-fourth of the filling on the dough, leaving a 1/2-inch edge at the top and bottom. Slice the square in half. Starting at a long end, roll each half into a cylinder from the outside in, and then cut each rolled half into six evenly sized pieces.
• In a small bowl, whisk the egg and milk. Arrange 12 rugelach on one of the prepared baking sheets. Brush with the egg wash, and bake until golden-brown, 16 to 21 minutes. Repeat with the remaining dough and filling. When cool, dust with confectioner’s sugar, if you like, before serving.