In a large bowl or the bowl of a stand mixer with the paddle attachment, dissolve the yeast in the warm water. Add 1/2 cup sugar, 1/2 cup of the butter, milk, salt, eggs and 2-1/2 cups of the flour. Beat until smooth. If using a stand mixer, switch to the kneading hook. Stir in enough remaining flour to form a stiff dough.
Turn the dough onto a floured surface and knead until smooth and elastic, about 6-8 minutes or knead with the mixer until smooth. Place into a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1-1/4 hours.
Deflate dough. Turn onto a floured surface and divide in half. Roll each piece into a 24-in. x 13-in. rectangle. Spread 2 tablespoons of butter and 1/3-1/2 cup peach preserves to within 1/2 in. of edges. If using orange zest, sprinkle over the preserves. Combine the cinnamon and remaining sugar. Sprinkle over preserves.
Roll up, jelly-roll style, starting with a long side. Pinch seam to seal. Place, seam side down. With a sharp knife, cut the roll in half lengthwise. Pinch one end together and twist the two strands together 3 or 4 times, keeping the cut edge facing upwards as much as possible. Pinch together the other end. Place onto a large greased baking sheet. Repeat with the second piece of dough.
Cover and allow to rise until puffy, about 30 minutes. If using almonds, scatter a few on top before baking.
Bake in a pre-heated 350° oven for 20-25 minutes or until golden brown. Remove from pans to wire racks to cool.
Yield: 2 loaves (20 slices each).
Optional Vanilla Glaze: 1 cup icing (powdered) sugar, 1 tsp. vanilla and 2-3 tsp. milk (or enough to make a glaze that will fall off a spoon). Combine and stir until smooth.