In a medium bowl, add 1 cup warm water, yeast, and a pinch of sugar and let rest for 5-7 minutes until fluffy.
In a large bowl, add the flour, remaining water, foamed yeast, oil, remaining sugar, and salt and stir until combined.
Knead the dough for about 4-5 minutes.
Cover the dough with a clean kitchen towel or plastic wrap and let it rest for 30 minutes at room temperature.
Once rested, punch it down to release the air from the dough. Knead 5-7 minutes additionally.
Transfer the dough to a lightly greased bowl, cover it with plastic wrap and let it rest for 10-20 min at room temp, until 20% risen.
Then transfer to the fridge and let rest 2-3 hours in the refrigerator, until almost doubled in size.
Drizzle a 10x15" baking pan with olive oil. Then transfer the dough into the pan and gently stretch it to the edges with your hands, as in the IG Reel.
Cover the pan with a clean kitchen towel or plastic wrap and let it rest until doubled in size, for 50-60 minutes.
Meanwhile, heat a skillet over high heat. Add 4 tbsp olive oil, add the onions, and reduce heat to medium high heat. Sauté the onions for 4-6 minutes, stirring consistently. When the onions turn light brown, add the worcestershire sauce and continue cooking for 2 minutes until a deep, caramelized brown. Transfer the onions into a bowl.
In the same pan, add two tbsp olive oil and the sliced mushrooms. Add salt and pepper, sauté until golden brown, 6-8 minutes and then remove from the heat.
Meanwhile, boil the water. Slice the russet potatoes very thin with a mandolin, leaving the skin on. In a bowl, add very hot water and the potato slices. Leave in the water for 10-15 minutes until just softened. Using a straining spoon, remove the potato slices and let dry fully on a clean kitchen towel.
Optional but recommended: sauté the potatoes to get them a little bit of crunch and caramelization.
Preheat the oven to 450F. Once the focaccia dough has rested, use your fingers and press to make impressions in the bread. At this point, the dough should cover the pan fully.
Sprinkle the fontina cheese evenly over the top. Spread the caramelized onions evenly over as well, and then scatter the potatoes and mushrooms. Sprinkle the fresh rosemary leaves and then drizzle olive oil and a sprinkle of salt if desired.
Place the pan in the oven and cook for 20-25 minutes until nicely golden brown. Remove from the oven, let it cool for 10 minutes, then slice and serve while hot.
Bread
Toppings
Assembly
Bon Appetit!
