To the bowl of a stand mixer, add 1/2 cup bread flour, instant yeast and 1/2 cup warm milk. Let stand for about 30 minutes until puffed up and risen.
Add the eggs and sugar. Mix together. Add the bread flour and salt. This will be stiff, almost a little crumbly and that is okay. Knead for 3-5 minutes.
Cut the softened butter into Tablespoon sized chunks. With the mixer running, add the butter a chunk at a time until all the butter has been added to the mixer. Knead the dough for 10 minutes until the butter is fully combined and the dough looks shiny and smooth. It should be sticky but not overly sticky at this point.
Transfer the dough to a large bowl. Cover and refrigerate for 4 hours or overnight.
While the dough is refrigerating, prepare the raspberry puree and the parchment paper (Directions for raspberry puree is below. Directions/pictures for cutting the parchment are in the post)
Once the dough has risen for 4+ hours, transfer to a countertop. Split dough into 16 pieces, about 75 grams per dough ball.
Shape bun: Take a piece of dough. Roll out into a small rectangle on the counter. Spread 1 teaspoon of raspberry puree in the middle. Sprinkle 12-15 semi-sweet chocolate chips on top of the raspberry puree. Fold the dough in half. Holding both ends, twist the dough and then swirl into a bun shape. Place on top of a piece of parchment paper and into a muffin tin. Repeat with remaining dough balls.
Cover the buns and let rise for another hour. Preheat the oven to 400 degrees.
Egg Wash: Scramble one egg together with a teaspoon of water and brush onto the risen buns.
Bake buns for 15-20 minutes until golden on top and baked all the way through. Enjoy!