Make the streusel

1. To make the streusel, In a small bowl, mix the flour, brown sugar and cardamom together until the sugar is evenly distributed in the flour.
2. Pour in the melted butter, then use a fork to toss the ingredients together. Stir everything together until the crumbs start to form.
3. Cover the bowl, and refrigerate the mixture until you’re done prepping the cake.

Make the dough

1. Measure out the sugar, and then sprinkle a pinch of it into a small bowl with the warm water and yeast. Stir to dissolve, and then set aside for about 5 minutes until the yeast is foamy.
2. Heat the milk in a small pan until you see bubbles at the edges. Cut up the butter then stir it into the hot milk to melt along with the rest of the sugar. When the butter is melted, crack in the eggs and beat them until you get a smooth mixture.
3.  Mix the flour and the salt in a large mixing bowl or a stand mixer and then make a well in the center. Pour the milk/butter mixture into the well, then the yeast mixture as well as the vanilla paste and lemon zest.
4. Stir the ingredients with a wooden spoon to make a shaggy dough.
5. For kneading, by machine, switch to the dough hook on your mixer and let the mixer run on low speed until you get a smooth, sticky, elastic dough, about 5 minutes To knead by hand: turn the dough onto a lightly floured surface, and use a bench scraper

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   to slap the dough down, then bring the edges towards the center. Repeat this motion for 10 minutes, until you have a smooth elastic dough. Resist the urge to add more flour. This dough will be quite soft, but most of the stickiness will go away after the dough has risen.
6. Cover the dough with plastic wrap and set aside to rise for about 90 minutes.  Meanwhile, make the poppy seed filling if you haven’t already.

Assemble the babka

1. Divide the dough into 2 pieces.
2. Line a sheet tray with a piece of parchment

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   .
3. Lightly flour a pastry cloth

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   or a clean kitchen towel.
4. Divide the dough in two parts. Sprinkle a little flour on one portion of the dough and then roll out the dough into a rectangle about 11” x 14”.
5. Spread about 1/2 cup of the poppy seed filling over the dough.
6. Roll the dough over itself on the long edge into a tight log.
7. Pinch the seam on the bottom of the log to seal it well, and then tuck the ends under or pinch the rolled edges of the seam well so that the filling does not leak out during baking.
8. Place the dough log onto the parchment

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   lined sheet tray.
9. Cut through the log from the center to the end.  This will expose all the layers of filling.  Rotate the dough pieces upwards so that you can see the filling, and then twist the two pieces of dough together to make a twist.
10. Turn the baking pan around and then cut through the second half of the log from the center to the end.  Twist these two pieces together.
11. Repeat the rolling and filling for the second piece of dough.
12. Cover the logs with a clean kitchen towel to rise for 45 minutes.
13. Towards the end of the 45 minutes, preheat the oven to 350 F (180 F).
14. Just before baking, beat together the egg and milk to make an egg wash.  Brush the logs well with the egg wash.  Brush on the egg wash down the exposed stripes of dough rather than across them to avoid smearing the filling.
15. Sprinkle the logs with plenty of streusel (you can freeze any that is left over).
16. Bake the logs for 20-25 minutes until the dough is set and the middle springs back when you touch it.
17. Allow the logs to cool completely before slicing.
18. Store the babka at room temperature for up to 3 days or freeze the baked logs for longer storage.