The dough in the recipe given here produces a thick, tender focaccia with a crisp surface, which you can top with sautéed onion in the Genoese style, as described below, or vary in one of the alternative ways indicated, or devise a suitable variation of your own. – Marcella Hazan

Ingredients

For the dough

• 1 package active dry yeast
• 2 cups lukewarm water
• 6½ cups unbleached flour
• 2 tablespoons extra virgin olive oil
• 1 tablespoon salt

For baking the Focaccia

• A heavy-duty rectangular metal baking pan, preferably black, about 18 by 14 inches or its equivalent
• Extra virgin olive oil for smearing the pan
• A baking stone
• A mixture of ¼ cup extra virgin olive oil, 2 tablespoons water and 1 teaspoon salt
• A pastry brush

For the onion topping

• 2 tablespoons extra virgin olive oil
• 4 cups onion sliced very, very thin

Instructions

1. Dissolve the yeast by stirring it into ½ cup lukewarm water, and let it stand about 10 minutes or slightly less.
2. Combine the yeast and 1 cup of flour in a bowl, mixing them thoroughly. Then add the 2 tablespoons olive oil, 1 tablespoon salt, ¾ cup water, and half the remaining flour. Mix thoroughly until the dough feels soft, but compact, and no longer sticks to the hands. Put in the remaining flour and cup water, and mix thoroughly once again. When putting in flour and water for the last time, hold back some of both and add only as much of either as you need to make the dough manageable, soft, but not too sticky. On a very damp, rainy day, for example, you may need less water and more of the flour.
3. Take the dough out of the bowl, and slap it down very hard several times, until it is stretched out lengthwise. Reach for the far end of the dough, fold it a short distance toward you, push it away with the heel of your palm, flexing your wrist, fold it, and push it away again, gradually rolling it up and bringing it close to you. It will have a tapered, roll-like shape. Pick up the dough, holding it by one of the tapered ends, lift it high above the counter, and slap it down hard again several times, stretching it out in a lengthwise direction. Reach for the far end, and repeat the kneading motion with the heel of your palm and your wrist, bringing it close to you once more. Work the dough in this manner for 10 minutes. At the end, pat it into a round shape.
   Food processor note – The preceding 2 steps may be carried out in the food processor, but the hand method, aside from the physical satisfactions it provides, produces a focaccia with better texture.
4. Smear the middle of the baking sheet with about 2 tablespoons olive oil, put the kneaded, rounded dough on it, cover it with a damp doth, and leave it to rise for about 1½ hours.
5. For the topping: Put the 2 tablespoons of olive oil and all the slicked onion in a sauté pan, turn the heat on to medium high, and cook the onion, stirring it frequently, until it is tender, but not too soft. It should still be slightly crunchy.
6. When the indicated rising time has elapsed, stretch out the dough in the baking pan, spreading it toward the edges so that it covers the entire pan to a depth of about ¼ inch. Cover with a damp towel and let the dough rise for 45 minutes.
7. At least 30 minutes before you are ready to bake, put the baking stone in the oven and preheat oven to 450°.
8. When the second rising time for the dough has elapsed, keeping the fingers of your hand stiff, pop the dough all over, making many little hollows with your fingertips. Beat the mixture of oil, water, and salt with a small whisk or a fork for a few minutes until you have obtained a fairly homogenous emulsion, then pour it slowly over the dough, using a brush to spread it all the way out to the edges of the pan. You will find that the liquid will pool in the hollows made by your fingertips. Spread the cooked onion over the dough, and place the pan on the middle rack of the preheated oven. Check the focaccia after 15 minutes. If you find it is cooking faster on one side than another, turn the pan accordingly. Bake for another 7 to 8 minutes. Lift the focaccia out of the pan with spatulas, and transfer it to a cooling rack.
9. Serve focaccia warm or at room temperature that same day. It is preferable not to keep it longer, but if you must, it is better to freeze than to refrigerate. Reheat in a very hot oven for 10 to 12 minutes.