Onion Tart with Bacon & Egg

Method

1. Pre-dough (15 min). Whisk both flours in a mixing bowl and make a well. Dissolve the yeast and ½ tsp sugar in 25 ml lukewarm water, pour it into the well and pull in just enough flour to make a thick batter. Cover and let stand 15 min somewhere warm, until the surface looks puffed and a bit spongy.
2. Make and rest the dough (~10 min + 20 min). Add ~38 ml warm water, 25 ml lukewarm milk and ½ tsp salt. Knead until smooth and elastic (dough hook 6–8 min, or by hand 8–10 min); it should just start to pull cleanly from the bowl. Cover and let rest 20 min, warm.
3. Line the pan (15–20 min). Lightly butter a 26 cm / 10-inch springform, or line the base with parchment. Roll the dough to ~3 mm thickness, big enough to climb the sides. Fit it into the pan and form a rim ~3 cm (1¼ in) high. Dock the base with a fork and let it relax 15 min while you cook the topping.
4. Cook the onion–bacon mix (~25 min + cooling). Melt the clarified butter over medium heat. Add the bacon and cook 3–4 min, just until it renders a little (reserve a few nice strips for the top, optional). Add the onions and a good pinch of salt and sweat ~20 min, stirring now and then, until soft and translucent, no browning. Tip into a colander, drain, and cool to just warm. Preheat the oven to 220 °C / 425 °F now, rack in the middle.
5. Mix the custard and assemble (5 min). Whisk eggs and sour cream until smooth. Season with ½ tsp salt, several grinds of pepper, a pinch of nutmeg and ½–1 tsp caraway. Spread the cooled onion–bacon mixture evenly over the dough, pour the custard over it and jiggle the pan to level. Lay on the reserved bacon strips if using.
6. Bake (35–40 min). Bake on the middle rack until the rim is deep golden and the center is just set; a slight wobble is perfect. Rest 10 min, release the ring, slice and serve warm with a green salad, or let cool to room temperature.

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