These buns are mixed, shaped and allowed to rise in the refrigerator for 12 to 24 hours. The cool rise adds extra flavor; it also offers flexibility in timing. You can start them one day and bake them in the cool of the next morning, or start them before you leave for work and finish them just before your evening meal.
Toast the seeds: Place the sesame seeds, poppy seeds, flax seeds, and caraway seeds in a skillet. Cook over medium-low heat, stirring often, until the sesame seeds have turned golden brown, about 10 minutes. Remove from the heat and cool.
To make the dough: In a large bowl, stir yeast into water to soften. Add honey, salt, shortening and cooled seeds. Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Add 2 cups flour to the yeast mixture.
Beat vigorously for 2 minutes. Gradually add flour, a little at a time, until you have a dough stiff enough to knead.
Turn dough out onto a floured surface. Knead, adding flour as necessary, until you have a smooth, elastic dough.
Leave the dough on work surface. Cover with a towel and let rest for 10 minutes.
Divide the dough into 12 equal pieces. Shape each piece into a ball. Cover the balls with a towel and let rest for 5 minutes.
Lightly grease or line a baking sheet with parchment paper.
Flatten each ball into a 3 1/2" circle. Make them slightly concave in the center. Place 1/2" apart on the baking sheet.
Brush the tops lightly with vegetable oil, and lay a piece of plastic wrap over the buns. Cover the wrap with a cloth towel.
Refrigerate for 12 to 24 hours.
When you're ready to bake the buns: Preheat the oven to 400°F. Remove the buns from the refrigerator and let sit, covered, at room temperature.
Bake for 20 minutes, or until done. Immediately remove buns from baking sheet and cool on a rack.
Store, well-wrapped, for 4 days at room temperature, or freeze for up to 3 months.
