Add the yeast, water, and 1 tsp sugar to a large bowl (or the bowl of a stand mixer if you're using one).
Chop the oranges in half, then into quarters. Cut off the stem parts at the two ends but don't bother peeling them.
Add milk, butter, and sugar to a microwave-safe bowl and microwave in 30-second intervals until the butter is mostly melted.
Add the oranges (peels and all) and the milk mixture to a blender. Briefly blend. Add the eggs and salt, and blend on high speed until everything is is pureed and the consistency is smooth. (I used my Blendtec on the smoothie mode.)
Add the blended mixture to the bowl with the yeast. Add half of the flour and all of the raisins (optional), and stir to incorporate (or knead with your dough hook if you're using a stand mixer).
Keep adding flour about a cup at a time until the dough comes together into a ball—it should be pretty tacky but not crazy sticky. Knead for 8–10 minutes in a mixer, and about five minutes longer if kneading by hand.
Grease the bowl and leave the dough inside, covered with a damp towel or plastic wrap, to rise for about an hour.
The dough should now be doubled in size. Put it down on a flat counter and punch it down really really well.
Cut into pieces. 16 pieces for small breads (ramekin-sized), 8 for medium-sized cans, 4 for loaves. Shape into whatever shapes you want (see the pictures further down in this post for some ideas).
Grease whatever pans you're using, and put in the dough. Let rise for another hour.
Preheat the oven to 350 °F. For small breads, bake for about 25 minutes. For medium breads, about 30 minutes, and for loaves, about 45 minutes.
Remove the breads from the oven and allow to cool for a couple minutes inside their pans. Then transfer them to racks until fully cool.