M.A. Kitchen
Step 1: Mix bread ingredients (except egg yolk) in a stand mixer for 8-10 minutes until smooth.
Step 2: Shape dough into a ball, let it rise for 1.5 hours until doubled.
Step 3: Flatten dough into a 1-inch thick square.
Step 4: Roll the dough into a log, let it rise for an hour, then preheat the oven, brush with egg yolk, and bake until dark brown.
Step 5: Cool, slice, and spread with buttercream before enjoying.