Start by grinding your poppy seeds in batches in a spice grinder or coffee grinder, or by hand with a mortar and pestle. Make sure the poppy seeds are very fresh, give them a good sniff – they should not smell musty. Poppy seeds have a lot of oil and can quickly turn bad on the shelf. A food processor can also work for grinding the poppy seeds, but it won’t be as finely ground as it is in a spice/coffee grinder. By grinding the poppy seeds you will not only end up with a smoother filling, but you will help your filling mixture thicken when you add the liquid ingredients.

In a small pot on medium heat, melt the butter, then add the milk, sugar and honey. Stir until the sugar is just dissolved and the mixture is very hot but not boiling.

Pour the milk mixture over the poppy seeds and stir. Add the vanilla; salt and stir until everything is well incorporated. Your mixture might seem a little soupy at this stage, but place it in the refrigerator to cool as you make the dough and let it rise. You can also make the filling 1 or 2 days in advance and store it in the fridge.

In the bowl of a stand-mixer fitted with a dough hook, add the yeast and a teaspoon of sugar. Heat the milk until warm, and add the milk to the bowl. If making by hand, add the milk, yeast and sugar to a small bowl. Allow the yeast to become foamy and bubbly, about 5-8 minutes.

Add the beaten eggs, melted and cooled butter, sugar and salt to the milk and yeast. Turn mixer to stir and slowly add the flour to the liquid until all of it is incorporated. If making by hand, add the flour to a large bowl, make a well, then add the milk mixture and the remaining ingredients and combine until everything is incorporated.

Once the flour is incorporated, turn the mixer to medium and allow the dough to form into a silky smooth and soft ball, about 8-10 minutes. The dough will be sticky, but the longer it is worked the smoother it will get, and it will stop sticking to the sides of the bowl or to your hands when you touch it. By hand, knead the dough until very smooth, soft and no longer sticking to your hands.

Gently transfer the dough into a large lightly oiled bowl and cover with a damp clean kitchen towel. Allow the dough to rise for 1-1 1/2 hours, or until the dough has doubled in size.

Once the dough has risen, divide it in two. Lightly dust your surface. I like to roll the dough directly onto a piece of parchment paper – this will help you shape the dough and transfer it onto baking sheet more easily. Roll out each half of dough to about a 12-by-16-inch rectangle – or the size of a baking sheet. Add half of the poppy seed filling to each half of the dough. Spread it in an even layer, leaving a 1-inch border around the edges of the dough.

Carefully begin to roll up the dough. Once you’ve reached the edge, brush it with a little of the egg wash to help seal it shut. Pinch the edge of the roll together to ensure that the filling doesn’t leak; also pinch closed each end of the roll so they do not leak either. Carefully transfer the roll seam side down onto the baking sheet. Make slits in the top of the dough; this will help keep the poppy seed roll from bursting. Repeat the process with the second half of the dough.

Preheat the oven to 350 F. Cover the rolls with a clean kitchen towel or a loose piece of plastic wrap and allow to rise again for 30 minutes. Before going in the oven, generously brush the pastry with the egg wash. Make sure the oven racks are on the top and lower thirds of the oven, and place each baking sheet on one of the racks.

Bake for 30-40 minutes, rotating the rolls once after 15 minutes. Bake until deep golden brown. Allow to cool, then slice and serve. Poppy seed rolls can keep up to 5 days in an airtight container.