Directions

1. In the bowl of your stand mixer, mix together with a wooden spoon 1/4 cup flour, yeast and 2 tablespoons water. Allow the sponge to rest for 15 minutes.
   
2. In a small bowl add 2 3/4 cups flour, potato flour, and salt then whisk together. Set aside.
   
3. In the stand mixer add the pineapple juice, butter, brown sugar, 2 eggs and 1 egg yolk, and vanilla, mixing on low with paddle attachment until well combined. Slowly add bowl of flour into the wet ingredients. Mix for 3 minutes with paddle attachment then switch to dough hook and knead until the dough is cohesive and smooth for 5 minutes; it'll be very sticky at first. If you find the dough isn't coming together, add a tablespoon or two of flour.
   
4. Lightly grease the mixing bowl; round the dough into a ball, and place it in the bowl. Cover, and let rise until very puffy, about 1 1/2 to 2 hours.
   
5. Lightly grease a 9" x 13" pan. Gently deflate the dough. Divide it into 16 equal pieces, by dividing in half, then in halves again, etc. Round each piece into a smooth ball. Space the buns in the pan.
   
6. Tent the dough gently with lightly greased plastic wrap. Let the dough rise in the pan for 1 hour, until it's nicely puffy. Toward the end of the rising time, preheat the oven to 350°F.
   
7. Mix the reserved egg white with 1 tablespoon water, and brush onto the surface of the rolls. Bake the rolls for 20 to 25 minutes, or until the internal temperature reads 190°F. Remove the rolls from the oven, and after a few minutes, turn them out onto a cooling rack.
   
8. Serve warm. Store leftovers, well wrapped, at room temperature for several days; freeze for longer storage.