Step 1
Place poppy seeds into a food processor and process until seeds are ground about 1 minute.
Step 2
Mix poppy seeds with 3/4 cup sugar 1 tablespoon melted butter lemon juice and hot milk in a bowl; stir to combine. Cover poppy seed filling and refrigerate while making bread (filling will set up and thicken as it chills).
Step 3
Mix yeast with water and 2 tablespoons sugar in a small bowl. Allow to stand until the yeast forms a creamy layer.
Step 4
Whisk flour with salt in a bowl; use a pastry cutter to cut 1/4 cup butter into the flour mixture until the mixture resembles coarse crumbs.
Step 5
Pour yeast mixture and egg yolk into flour mixture and stir to make a soft dough.
Step 6
Turn dough out onto a floured work surface and knead until smooth and slightly springy about 5 minutes. If dough is too sticky knead in more flour about 2 tablespoons at a time.
Step 7
Cut dough into 2 equal pieces. Roll each piece out into a 12x16-inch rectangle.
Step 8
Spread half the poppy seed filling over each rectangle leaving a 1-inch border. Fold the 1-inch border back over the filling on all sides and press down.
Step 9
Pick up the shorter side of a dough rectangle and roll it like a jelly roll; repeat with second rectangle. Pinch ends together or tuck ends under to prevent filling from leaking out.
Step 9
Line a baking sheet with parchment paper; place rolls seam sides down on the baking sheet and allow to rise in a warm place until doubled about 1 hour.