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Potato focaccia with red onion and sage cooling on a wire rack, topped with crisp golden potato slices

Potato Focaccia with Red Onion and Sage

Potato focaccia with mashed potato in the dough and a crisp topping of paper-thin potato, red onion and sage.
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Prep Time 30 minutes
Cook Time 30 minutes
Rising 2 hours
Total Time 3 hours
Servings: 12 pieces
Course: Appetizer, Bread, Side Dish
Cuisine: Italian, Scandinavian
Ingredients Equipment Method Notes

Ingredients
  

Dough
  • 250 g mashed potato 1 cup, cooled and unseasoned — about 2 medium floury or all-purpose potatoes (russet or Yukon Gold), boiled and riced
  • 450 g lukewarm water 1⅞ cups
  • 25 g fresh yeast or 7 g (2¼ tsp) instant dry yeast
  • 600 g bread flour about 5 cups — weigh it if you can, cup measures vary a lot
  • 15 g fine sea salt 2½ tsp
Topping
  • 200 g waxy potatoes Yukon Gold or another all-purpose potato — sliced paper-thin
  • 1 red onion halved and sliced thin
  • 15 small sage leaves
  • 3 tbsp olive oil plus more for the pan
  • flaky sea salt Maldon or similar
  • black pepper freshly ground, generously

Equipment

  • Mandoline slicer The topping only works if the potato is paper-thin — thicker slices stay raw under the crust. Use the hand guard, always.
  • 9x13-inch baking pan Our standard pan (23×33 cm). Straight sides give you the thick, airy edge, and metal browns the base better than glass.
  • Digital kitchen scale This dough is wet and forgiving, but the flour-to-water ratio is not. We bake everything by weight.
  • Potato ricer Gives a lump-free mash that disappears into the dough. A masher works, but rice it if you can.
  • Bench scraper For lifting and folding wet dough without working extra flour into it.
  • Parchment paper Lines the pan so you can lift the whole slab straight out onto a rack.
  • Wire cooling rack Lift the focaccia straight onto it so the base stays crisp instead of steaming soft.

Method
 

  1. Cook the potatoes. Boil the potatoes for the dough until tender, drain well and let the steam escape for a few minutes. Rice or mash them and let cool to lukewarm — hot potato will kill the yeast.
  2. Yeast and potato. Whisk the yeast into the lukewarm water. Add the mashed potato and stir until it breaks up.
  3. Mix the dough. Add the flour and salt and mix until no dry flour remains. There's no oil in this dough — the potato does that job. It will feel wet and sticky, and that's correct. Don't add more flour.
  4. First rise with folds. Cover and leave to rise until doubled, about 1 hour. Give it three sets of stretch-and-folds in the bowl during the first 45 minutes, using wet hands.
  5. Into the pan. Line the pan with parchment and oil it well. Tip the dough in, coat your fingertips in oil and gently press it out to the corners. Cover and proof until puffy and full of air, about 1 hour.
  6. Preheat. About 30 minutes before the dough is ready, heat the oven to 425°F (220°C), conventional.
  7. Prepare the topping. Slice the potatoes paper-thin on a mandoline and slice the red onion thin. Toss both with the olive oil, sage, a generous grind of black pepper and a pinch of salt
  8. Dimple and top. Dimple the dough all over with oiled fingertips, pressing right down to the bottom of the pan. Scatter the potato, onion and sage over the top in loose, overlapping layers — leave it uneven, the ruffled edges are what turn crisp.
  9. Bake. Finish with flaky salt and a last drizzle of oil. Bake for 30 minutes, until the potato edges are deep golden and the bread is baked through at the center.
  10. Cool on a rack. Lift the focaccia out on the parchment and cool on a wire rack for at least 15 minutes so the base stays crisp. Cut into 12 pieces.

Notes

Chef's tip — no oil in the dough. The cooked potato does the job olive oil would: it keeps the crumb soft and moist for days. Save the oil for where you can taste it — the pan, the dimples and the topping.
  • On the potatoes. We bake this with Jacky, a small, yellow-fleshed Norwegian variety that's floury enough to mash beautifully. In the US, Yukon Gold does both jobs well. What matters more than the variety is that the topping slices are under 2 mm — thin enough to crisp before they fall apart.
  • Slow rise option. Halve the yeast and leave the dough on the counter from breakfast until dinner, then shape, proof and bake. Longer fermentation, more flavor, same result.
  • Cold proof. The dough also takes an overnight rest in the fridge after mixing, up to 12 hours. Let it come back to room temperature before pressing it into the pan.