WHAT YOU'L NEED
For the dough:
1/2 cup whole milk, warmed
2 1/4 tsp (1 envelope) active dry yeast
1/3 cup granulated sugar
1 large egg
1 large egg yolk
½ teaspoon kosher salt
2 cups all-purpose flour, plus more for dusting
6 tablespoons (85 grams) unsalted butter, cut into pieces and brought to room temp, plus more for greasing bowl
For the filling:
1/3 cup strawberry jam
1 Tbs balsamic glaze
1/2 tsp fresh cracked black pepper
1/4 tsp kosher or flake salt
For optional sugar syrup glaze:
2 Tbs sugar
2 Tbs water
WHAT YOU'LL DO
Pour warm milk into a pyrex or small bowl; sprinkle the yeast over milk. Let it stand until foamy (bloomed), around 5 minutes.
Whisk the egg, egg yolk, and 1/3 cup granulated sugar in a medium bowl until smooth. Then whisk in yeasty milk mixture.
Combine the 1/2 tsp kosher salt and 2 cups flour in the bowl of an electric mixer with the paddle attachment. Add the egg/milk mixture and beat on low until nearly incorporated. Switch to the dough hook and add in the pats of butter; beat on medium-low until butter is completely incorporated. Keep mixing until the dough is smooth, shiny and just slightly sticky, almost 10 minutes.
Turn out dough onto a lightly floured surface and knead by hand just a few times (dough will still be wet and a little sticky) and shape into a ball. Butter/ grease a large mixing bowl and transfer dough to it. Cover with plastic wrap and let rise in a warm place until doubled in size, 1.5 to 2 hours. Once it has doubled in size, transfer to the fridge to chill for another 30 minutes (this may seem like an annoying extra step but it makes your dough so much easier to work with).
Filling and Assembly
Generously butter loaf pan, or lightly grease and line with parchment with the parchment extending out two sides, to make it easy to lift the babka out later.
Turn out the chilled dough onto a large, lightly floured surface. Roll out into a large rectangle (about 12 x 18-20 inches). Using a spatula or back side of a spoon, spread the strawberry jam evenly across the surface. Then drizzle the balsamic glaze on top of the jam. Sprinkle the black pepper and salt evenly. Roll up dough in the direction of the long side (starting with the 12 inch end), pulling lightly on it as you roll to maintain thickness.
Cut the log in half lengthwise. Maneuver the halves side by side, cut side up, so they are touching. Your hands will get sticky with jam and this will be a terrible mess but try to keep the filling in the dough. Place one half over the other to make an X, then twist the two ends on each side of the X once or twice if you can. (You should have a minimum of 3 twists.) Transfer the bread as best as you can to the prepared loaf pan, cover with plastic wrap, and let rise another 30 minutes at room temp.
Preheat your oven to 350 degrees.
Bake babka in the preheated oven, rotating pan halfway through, until golden brown, 50–60 minutes.
Optional: for that classic shiny babka glaze, while the babka is baking, you can combine 2 Tbs of sugar with 2 Tbs of boiling water. Stir until the sugar is completely dissolved. Let cool and as soon as the babka comes out of the oven, brush the sugar syrup over the top and corners to give it a gorgeous sheen and the perfect finish.
Transfer the pan to a wire cooling rack and then after 15 minutes turn out onto rack, running a paring knife around edges to help loosen if needed.
Let cool completely before slicing. It will keep fresh for two days at room temp, although i doubt it will last that long. And I would definitely not recommend you make day-two french toast with it. I mean who would suggest such a ridiculous idea.