In large bowl of electric mixer, stir yeast into pineapple juice until dissolved. Let stand until foamy, 5 to 10 minutes. Add sugar, potatoes, eggs, 1/4 cup butter, salt, vanilla, ginger and 2 to 2 1/2 cups flour. Beat at medium speed with electric mixer 4 minutes or, beat 400 vigorous strokes by hand. Stir in enough remaining flour to make a stiff batter. Cover with a slightly damp towel. Let rise in a warm place, free from drafts, until doubled in bulk, about 1 hour. Grease 2 (9"x5") loaf pans or 2 (2 quart) casseroles; set aside. Stir down batter. Turn into prepared pans. Butter your fingers and 2 (12") squares of waxed paper. Smooth batter with your buttered fingers. Cover with buttered waxed paper. Let rise until doubled in bulk, about 45 minutes. Preheat oven to 375 degrees. Bake 30 to 40 minutes or until bread sounds hollow when tapped on bottom. For browner bottom crusts, remove from pans. Place directly on oven rack during final 5 minutes of baking. Brush melted butter over tops. Cool on racks. Makes 2 loaves.