Sweet Caramelized Onion and Parmesan Challah

This recipe is something between a yeast cake and a sweet challah: a soft, puffy dough filled with onions caramelized slowly until sweet, plus Parmesan cheese, all topped with nigella seeds for crunch and flavor. A tall, impressive yeast challah that will be the star of your Shavuot table.

Ingredients for sweet caramelized onion and Parmesan challah (9½-inch / 24 cm or 10-inch / 26 cm springform pan)

For the yeast dough

• 1 large egg, at room temperature.
• 600 g all-purpose flour (4 cups + 4 tablespoons).
• 10 g instant dry yeast (1 tablespoon).
• 100 g sugar (½ cup).
• 60 g vegetable oil (¼ cup).
• 250 ml water (1 cup + 1 tablespoon).
• ¼ teaspoon salt.

For the filling

• 2 large onions + 3 tablespoons vegetable oil.
• About 50 g grated Parmesan cheese (you can use less).
• 60 g soft butter.

For the topping

• 1 beaten egg.
• Nigella seeds.
• A handful of grated Parmesan cheese.

Instructions

1. Start with the dough: in the bowl of a stand mixer fitted with the dough hook, combine the flour, yeast and sugar. Add the egg, water, oil and salt, and knead for about 10 minutes, until you have a smooth, slightly sticky dough.
2. Grease a wide bowl and put the dough in it. Cover well and let it rise at room temperature for about an hour.
3. Caramelizing the onions: put the oil in a wide skillet and heat it over low heat. Peel the onions and cut them into thin strips. When the oil is hot, add the onions and caramelize them over low heat until golden (caramelizing onions takes time, so stir from time to time and let them caramelize well). Let them cool and drain off the oil.
4. Dust a work surface with a little flour, put the ball of dough on it and roll it out into a square. Spread the soft butter over it in an even layer, scatter the caramelized onions over it, and finish with a generous sprinkle of Parmesan. Roll it up into a long, thin rope, pinch the seam closed firmly, and coil it into a spiral (you can shape the spiral directly in the pan, so you won't need to lift the dough afterward).
5. Grease the pan with a little butter and put the challah in it. Cover and let it rise at room temperature for about 30 minutes.
6. Brush with beaten egg, and sprinkle with a little Parmesan and nigella seeds.
7. Bake in an oven preheated to 350°F (180°C) for about 40 minutes, or until browned.
8. Let it cool and release it from the pan.