Sponge
1/4 cup (28g) All-Purpose Flour
1 tablespoon instant yeast
2 tablespoons (28g) water
Dough
1/2 cup (113g) pineapple juice, canned
4 tablespoons (57g) unsalted butter, softened
1/3 cup (71g) brown sugar
2 large eggs plus 1 egg yolk, white reserved
1 teaspoon vanilla extract
2 3/4 cups (326g) All-Purpose Flour
2 tablespoons (21g) potato flour (you can use instant potato flakes)
1 1/4 teaspoons salt
For the sponge: In the bowl of your stand mixer, combine the sponge ingredients. Allow the sponge to rest for 15 minutes.
Add the pineapple juice, butter, brown sugar, eggs and yolk, and vanilla, mixing until well combined.
Whisk together the remaining flour, potato flour, and salt before adding to the liquid ingredients.
Mix and knead until the dough is cohesive and smooth; it'll be very sticky at first. If you're using a stand mixer, beat with the flat beater for about 3 minutes at medium-high speed; then scrape the dough into the center of the bowl, switch to the dough hook, and knead for about 5 minutes at medium speed. It may have formed a very soft ball, but will probably still be sticking to the bottom of the bowl. If you find the dough isn't coming together, add a tablespoon or two of flour.
Lightly grease a large 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.
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.
Tent the dough gently with 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.
Mix the reserved egg white with 1 tablespoon cold water, and brush some onto the surface of the rolls; this will give them a satiny crust.
Bake the rolls for 20 to 25 minutes, or until the internal temperature reads 190°F on a digital thermometer.
Remove the rolls from the oven, and after a few minutes, turn them out onto a cooling rack.
Serve warm. Store leftovers, well wrapped, at room temperature for several days; freeze for longer storage.
To make hamburger-sized buns, prepare the dough according to the recipe instructions, and after the rise divide it into six equal pieces. Round each piece into a smooth ball, and place them into a cookie sheet lined with parchment, flattening them gently. Let the buns rise for an hour, until they are nicely puffy, then brush the rolls with the egg wash, and bake them for 20 to 25 minutes until they're a deep golden brown.