Proof the yeast: Place 1/2 cup warm water in a small bowl, and sprinkle yeast over it. Stir to combine, and let sit until mixture becomes foamy, about 10 minutes.
In the bowl of an electric mixer fitted with the paddle attachment, combine egg yolks with remaining 1/2 cup warm water. In a medium bowl, combine salt, canola oil, honey, pumpkin, cinnamon, ginger, and allspice. Replace paddle attachment with dough-hook attachment, and add the pumpkin mixture to the mixer bowl; combine. Add the yeast mixture, stirring until combined.
Slowly add flour, 1 cup at a time, until all the flour is incorporated into dough. Transfer the dough to a lightly floured work surface, and knead the dough by hand for 10 minutes. Place dough in a lightly oiled bowl, cover with plastic wrap, and let rise until doubled in size, about 1 hour.
Transfer the dough to a lightly floured work surface, punch down the dough, and then form it into two 8-inch loaves. Place the loaves on a baking sheet lined with parchment paper, cover with a kitchen towel, and let rise until doubled in size, about 1 hour.
While the dough is rising, heat the oven to 350 degrees. Mix remaining egg yolk with 1 tablespoon water. Brush the loaves with the egg glaze, and bake until golden brown, about 50 minutes. Let cool on a wire rack, and serve.