Place yeast, sugar and warm water into the bowl of an electric mixer. Let stand for five minutes.

Add remaining dough ingredients, alternating wet and dry, and mix very well for at least five full minutes to make a soft dough. Cover and let rise for one hour, or until doubled.

Meanwhile, combine all ingredients for the filling in a large bowl and blend very well, using a dough hook, immersion blender or just the back of a fork (with a strong arm holding it!)

Mix ingredients for crumb topping as well, by simply crumbling butter, flour and sugar with your fingers to create a crumbly consistency. Set aside.

Preheat oven to 350 degrees Fahrenheit.

Once dough has risen, take challah (without a brachah; click here for more information on hafrashat challah) and divide the dough into three or four parts (depending on the size of your pans and how large you want your cakes to be). Roll each piece of dough out on a floured surface to about a quarter-inch thick, and smear with filling. Use up all the filling amongst the cakes.

Roll each piece of dough up in jelly-roll fashion, rolling gently so as not to squeeze out all the filling. Bend it to fit into a round pan, shaping it like a spiral or knotting it.

Brush the top of each babka with beaten egg and sprinkle generously with crumb topping. Bake for 45 to 50 minutes.