Place the potato chunks in a saucepan and add water to cover. Bring to a boil, reduce the heat to a simmer, and cook until tender, about 20 minutes. Drain, reserving the liquid; add water as needed to make 1 3/4 cups liquid. Mash the potato (no lumps pleas) to yield 1/2 cup and set aside. Cool both the potato water and the mashed potato to 105 to 115 degrees Fahrenheit. In a large bowl with a whisk or in the work bowl of a heavy-duty electric mixer fitted with the paddle attachment, sprinkle the yeast over the potato water. Stir to dissolve. Add the sugar, mashed potato, and 1 cup of the flour. beat until smooth and cover with plastic wrap. Let rest at room temperature until bubbly, about 45 minutes. Add the salt, eggs, oil, and 1 more cup flour to the batter and beat until smooth, about 1 minute. Add the raisins, currants, carrot or parsnip, and pineapple. Add the remaining flour, 1/2 cup at a time, until a soft dough is formed that just clears the sides of the bowl. Turn out the dough onto a lightly floured work surface and knead until smooth, shiny, and soft, about 2 minutes, adding only 1 tablespoon flour at a time as necessary to prevent sticking. Push back any fruits that may fall out during kneading. It is important that this dough remain soft and pliable, or it will be too dry. Place in a greased deep container, turn once to coat the top, and cover with plastic wrap. Let rise at room temperature until doubled in bulk, 1 1/2 to 2 hours. Turn out the dough onto the work surface and divide into 3 equal portions. Form each into a fat rectangular loaf. Place each portions into a greased 8-by-4 inch loaf pan. Cover loosely with plastic wrap and let rise at room temperature until doubled in bulk, or about 1 inch above the rim of the pans, 45 minutes to 1 hour. Twenty minutes before baking, preheat the over to 375 degrees Fahrenheit. Bake in the center of the preheated oven until the loaves are golden brown and sound hollow when tapped, 30 to 35 minutes. Remove immediately from the pans to a rack to cool completely before slicing.