Mix together water, sourdough starter, sugar, and salt in a straight edge container or medium bowl. Add in flour and mix until a shaggy dough is formed. Cover the dough and let sit at room temperature.350 grams water, 50 grams active and bubbly sourdough starter, 50 grams sugar, 10 grams salt, 500 grams bread flour
About 30 minutes later, perform a set of stretch and fold and then leave the dough to sit covered. I recommend doing this at least twice with about 30 minutes in between.
During the second set of stretch and folds add in the white chocolate chips and sliced almonds. Or if you prefer to add them during shaping you can do that too. 170 grams white chocolate chips, 55 grams almonds
Let the dough sit covered for 10-14 hours, until the dough is risen about 75%.
Make the butter mixture by mixing together the butter, powdered sugar, almond extract, and flour.70 grams butter, 30 grams powdered sugar, ½ teaspoon almond extract, 9 grams flour
Spread the dough out into a chubby rectangle on an unfloured surface. Spread half of the butter mixture over top the dough. Then bring the ends together meeting them in the middle. Add another layer of butter to the top and the remaining white chocolate chips and almond slivers and then roll the dough up into an oval shape. Pinch the seams closed and place the dough in a floured 8-10" proofing basket and cover.
Place the dough in the fridge for the second proof. Ideally you want to wait at least 8 hours but you can do it earlier depending on when you want to bake.
When ready to bake, preheat the oven and dutch oven to 450°F.
Score the dough and place it into the dutch oven. Bake covered for 25 minutes followed by 10-15 minutes uncovered or until golden brown and baked with an internal temperature of at least 205℉.
Remove the bread from the dutch oven and place on a cooling rack to cool.
Notes
The key when shaping dough with butter is to touch it as little as possible. If the dough is beginning to tear during shaping stop and let the dough rest for 10-15 minutes and then come back to finish. Do not over shape this! Shape it quickly and then stop handling it. Trust me, the more you work with it the more of a mess you will end up making. You want to keep the butter inside the dough as much as possible.
It is normal for a little bit of butter leakage to happen. To ensure it is minimal try to be super careful when shaping to keep the loaf from tearing open. If you are getting a lot of leakage add a little more flour to your butter mixture.
If you notice your loaf is getting too dark but is not done cooking you can reduce the heat to 425 degrees Fahrenheit and keep the lid on the loaf the entire time.