• In a bowl of a stand mixer, mix the flour, sugar and salt. Add the milk, eggs and active sourdough starter. Start mixing the dough with a bread hook attachment on low speed until you have a shaggy dough (about 5-7 minutes). Cover the bowl with a tea towel and let the dough rest for 10-15 minutes.
• Return the bowl to your stand mixer, and running it on medium heat, start adding room temperature butter one bit at a time. Note, that butter will tend to stick to the sides of the bowl, so you may need to scrape the sides once or twice. Run the mixer for 10-15 minutes until you have a relatively wet, but soft and elastic dough that passes the windowpane test.

Bulk Fermentation and Coil Folds:

• Scoop the dough into a lightly greased bowl, cover it with plastic wrap and leave it in a warm spot (20-24°C) for 4 hours.
• Over the first two hours, every 30 minutes, perform 3 series of coil folds. You will have a much less sticky dough by the end of the fourth coil fold. Then leave it to finish its first rise for 2 hours. Your dough is unlikely to double in size, but should increase by about a quarter.

Cold Proof:

• Place the sourdough babka dough in the fridge to finish proofing overnight. The dough ferments slower at cold temperatures, so it can safely stay in the fridge for 8-24 hours.

Filling and Shaping:

• The next day, start by preparing the strawberry cream cheese filling. Using an electric handheld mixer, beat the cream cheese and caster sugar until well combined. Mix in the freeze-dried strawberries, flour, salt, and zest of a lemon. Set the filling aside.
• Line a 2 lbs loaf tin with baking parchment.
• The next step is the trickiest one, but dust the surface with flour generously, and you'll be just fine. Work quickly, as it's a wet dough, but you have a benefit of it being cold and stiff from a night in the fridge.
• Scoop the dough onto a floured work surface. Roll it out into a large rectangle measuring about 20x40cm (8×16 in).
• ​Spread the strawberry filling on the surface, then roll it into a very tight roll starting from the long side.
• ​Cut the roll in half lengthways using a sharp knife, but leave it intact at one end (so you have two legs attached at the top).
• Twist the two legs together. Then place it into a prepared loaf tin (make sure to fit it in snuggly and don't worry if you have to serpentine the braid on top for a second layer).

Second Proof:

• Brush a piece of plastic wrap (cling film) with neutral oil. Cover the top of the sourodugh babka loosely and leave it at a warm temperature (21-27°C) to proof again for 2.5-3 hours. The loaf should puff up by about 20-25% in that time.

Baking:

• Preheat the oven to 170°C Fan (340℉).
• Make an egg wash by mixing an egg yolk with a tablespoon of milk. Brush it on the surface of the babka gently.
• Bake Strawberry Babka in the oven for 55-60 minutes. It should puff up heaps and turn golden brown! If it is browning too much, cover the top with the foil towards the end of baking.

Simple Syrup (Optional)

• Whilst the babka bakes, make a sugar syrup. In a small saucepan mix 30 g caster sugar and 30ml water together. Heat it over low heat, stirring until sugar dissolves, then let the syrup bubble, and take it off heat. Once your baba is cooked, using a pastry brush, brush the syrup all over the top of the babka.
• Let the cinnamon babka firm up in the loaf tin for 15-20 minutes, then take it out of the tin, and transfer it onto a wire rack to cool completely.