Prepare the dried blueberries: Set aside about 30-50g of whole dried blueberries to add directly to the dough. Take the remaining 50-70g of dried blueberries and rip them into smaller pieces. This will help incorporate the blueberries into the dough without causing tearing to occur later. I like to target about 30g of whole blueberries and 70g blueberry pieces.
100 g dried whole blueberries
Mix the dough: In the bowl of a stand mixer add the flour, water, salt, sugar, milk, sourdough starter, butter, water, dried blueberries, and optional active dry yeast. Mix on low speed with the dough hook attachment for 1 minute. Add the softened butter and continue mixing, scraping down the sides as needed, until a shaggy dough forms (about 3-4 minutes).
605 g all-purpose flour, 66 g granulated sugar, 12 g kosher salt, 60 g sourdough starter, 214 g water, 120 g whole milk, 100 g dried whole blueberries, 1.5 g Optional: active dry yeast, 57 g unsalted butter
Add purple sweet potato paste (for marbling): Remove the shaggy dough from the dough hook and lay it out on a work surface. In a small bowl, mix together 6g of the purple sweet potato flour and 6g water to form a paste. It will be clumpy. Add the clumps of sweet potato paste to the top of your dough. Don’t worry about making it look pretty now. Flip over the dough so the side with the purple paste is against the table. Knead the dough by hand for about 3 minutes, until you achieve your desired purple webbing pattern. There’s no right or wrong pattern, have fun with it! At this point, you can also sprinkle crushed dried blueberries on top of the dough.
6 g purple sweet potato powder (mixed with 6g water), 20-40 g Optional: freeze-dried blueberries, crushed
First Rise: Shape the dough into a ball and place in a bowl, cover, and let rise at room temperature for 3-4 hours. Once your dough has increased in volume by roughly 1.5x, transfer it to the fridge for 4 - 12 hours.
Prepare the butter block: Here’s a great video of Claire Saffitz showing you how to make a butter block. Lay out a large sheet of parchment paper. Place your sticks of butter next to each other in the center of the paper, then fold the sides of the parchment over to fully enclose the butter. Flip over the parchment paper so the folded sides are against the table. Using a rolling pin, lightly beat the butter into a ½’’ thick layer. Remove the butter from the parchment paper, and re-wrap the butter, measuring the parchment paper so that it forms an 8’’ square. Your ½’’ butter layer should be smaller than the 8’’ parchment paper square at this point. Fip the packet over so the folds are against the table and beat the butter into an 8’’ by 8’’ square. Eventually, it will be easy to roll the butter with your rolling put to fill out the edges of the parchment paper and get a clean square shape. Be sure to remove any air bubbles. Place the butter block in the fridge to firm up. 340 g unsalted butter (84-86% butterfat)