Additional desired toppingsoptional, see above post for ideas
In the bowl of a standing mixer or a large mixing bowl, stir together the all purpose flour, whole wheat flour, yeast, and salt. Drizzle with 1/4 cup olive oil. Heat the water to the temperature specified by the yeast manufacturer (check your packet; some brands call for 110 degrees F; others up to 130 degrees F).
With a hand mixer or the stand mixer’s paddle attachment, beat dough on low speed while gradually pouring in the water. Slowly increase the speed to high, then beat for 1 minute. The dough will be very sticky.
Transfer to a clean, lightly oiled bowl, turn once to coat, then cover with plastic. Let rise in a warm, draft free plate for 1 to 2 hours, until the dough becomes puffy, or store in the refrigerator for up to 3 days.
Meanwhile, prepare any desired focaccia toppings.
Place a rack in the upper third of your oven and preheat the oven to 375 degrees F. Drizzle a large baking sheet generously with olive oil. Gently turn the risen dough out onto the greased baking sheet. Coax and stretch the dough into to a 1/2-inch thick oblong shape (it may not be uniform), then cover with lightly oiled plastic and let rest 15 minutes.
With your fingertips, “dimple” the dough by poking it gently all over. Generously drizzle additional olive oil over the top of the dough, then sprinkle evenly with flaky salt. Add any other desired toppings (see blog post above for suggestions).
Bake until golden brown, 20 to 25 minutes, checking at the 18 minute mark. Serve warm or at room temperature.
This no knead focaccia is best eaten the day it's made. However, leftovers may be stored at room temperature, wrapped tightly in plastic wrap, for up to 1-2 days.
No knead focaccia keeps beautifully in the freezer. Slice it into pieces and store it in a freezer-safe container or gallon-size plastic bag for up to 3 months.
You can reheat frozen focaccia by defrosting it overnight in the fridge and then warming it on a baking sheet at 300 degrees F for 5-10 minutes.
A traditional French Provencal topping for focaccia is caramelized onions, pitted black olives, and a pinch of red pepper flakes. To caramelize onions: Heat 1 tablespoon olive oil in a very large skillet over medium heat. Add the onions and a pinch of salt, then sauté until they begin to soften, about 5 minutes. Reduce heat to low and let cook for 20 to 30 minutes more. until deep brown, sweet, and tender, stirring occasionally. Stir in a pinch of red pepper flakes.