In a medium bowl, combine yeast, 1 tablespoon flour, 1 tablespoon sugar, and 2 to 3 tablespoons warm water (100 to 110 degrees F). Mix until smooth. Set bowl aside until mixture is bubbly, 10 to 15 minutes.
Add 4 cups flour and milk to yeast mixture. With a wooden spoon, mix until well combined. Cover with plastic wrap and let rise at room temperature until double in size, about 30 minutes.
In the bowl of a heavy duty electric mixer fitted with the whisk attachment, beat 3 eggs, 8 egg yolks, and 2/3 cup sugar until light and pale yellow, about 5 minutes. Add the mixture to risen dough. Add salt, vanilla extract, lemon zest, orange zest, rum or brandy, melted butter, and vegetable oil. Whisk on medium speed until combined.
Remove whisk attachment from machine, and fit with the dough hook attachment. With mixer on medium-low speed, gradually add enough of the remaining 8 cups flour until dough comes away from side of bowl. Transfer dough to a clean work surface. Knead dough, adding any remaining flour if necessary, until smooth and elastic, 5 to 10 minutes. Transfer dough to a large bowl and cover with a cloth or plastic wrap. Place in a warm spot away from drafts and let it rise until double in size, 1 to 2 hours.
Place rack in lower 2/3 of oven and heat to 350 degrees F.
Butter 2 (9-inch) round cake pans. Cut 2 pieces of waxed paper about 2-inches longer than the circumference of the cake pans. Fold this in half lengthwise to make a double thickness. Place I piece inside each cake pan, patting it to adhere to the butter. The collar should extend 3 to 4 inches above the rim of the cake pan. Seal the 2-inch flap with more butter.
When dough has doubled in bulk, punch down and set aside 1/3 of dough in a medium bowl covered with plastic wrap, for decorations. Divide remaining 2/3 dough evenly between cake pans. Place bowl and saucepans of dough in a warm place to rise for about 30 minutes.
On a clean work surface shape reserved dough into desired motifs such as cross, rosettes, birds, braid, scrolls, etc. Keeping any dough that is not being used covered with plastic to prevent it from drying out. Brush surface of risen dough in saucepans with 3 lightly beaten egg whites. Attach decorative dough ornaments, using a toothpick if necessary to secure to loaves. Place in a warm place to rise until it reaches almost the top of pans, 20 to 30 minutes.
In a small bowl, whisk together remaining 3 egg yolks and 1 tablespoon water. Brush egg mixture on surface of loaves. Bake for 10 minutes, lower the oven temperature to 325 degrees F and bake for an additional 50 minutes. Cool bread in pans 30 minutes. When bread has cooled but is still warm, gently remove from pans and transfer to a rack to cool.
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