Starter

Cup of Yum
1. Make this starter the evening before you wish to bake. Place the potatoes in a medium pot and cover with an inch of cool water. Bring to a boil and cook until soft. Reserve 3/4 cup of the cooking water.
2. Drain the potatoes and mash until smooth. Add the potato water and flour and mix into a smooth paste. Transfer to a bowl and cool. Cover, and leave this starter in a warm place for 12 hours.

Mix the Dough

1. In a small bowl, whisk together the warm milk and the yeast. Set in a warm place to proof, about 7 minutes.
2. In the bowl of a stand mixer fitted with the paddle attachment, beat the egg yolks and sugar until pale yellow. Zest in the orange.
3. Scrape in 1 1/2 cups the potato starter and mix well. Tip in the proofed yeast, add the salt and mix gently.
4. Switch to the dough attachment and add 5 1/2 cups of the flour, 1 cup at a time. Mix until you have a rough, shaggy dough. Drop in the butter and mix well.
5. Remove the dough hook, cover the bowl with a tea towel and set in a warm place to rise for 1 hour.
6. After rising, return the bowl to the mixer and add the dough hook. Knead the dough on low for 10 minutes until smooth and elastic. Gradually add in the remaining flour. Again, set the dough to rise for an hour in a warm place.

Shape the Dough

1. Generously oil the clean tomato tins. Divide the dough into 3 pieces. Roll them into balls and tuck into the tins. Tins should be filled halfway with dough. If you have extra dough, fill a smaller tin or mini loaf pan. Cover the tins with a towel and set to rise in a warm place for one hour.
2. Preheat the oven to 350°F and set the oven rack on the bottom shelf. Place the tins on a baking tray and pop in the oven. Bake for 40-50 minutes until dark golden on top.
3. Cool the bread for 5 minutes in the tins (any longer and they will get soggy), then run a knife around the edges and pop them out to cool on a wire rack.

Glaze the Paska

1. In a small bowl, whisk together the orange juice, powdered sugar and vanilla until smooth. It should be runny and drip from the whisk. Brush or spoon over the tops of the cooled paska, letting the glaze drip down the sides. Garnish with a few sprinkles.