Mix. To a large bowl, add 4 cups All-purpose flour, 2 tsp Kosher salt, 2 tsp Instant yeast, 2 tbsp Extra virgin olive oil and 2 cups Lukewarm water. Mix with a wooden spoon until all the flour is hydrated. The mix should be shaggy but not sloppy.

Rise. Drizzle some olive oil over the top of the dough, cover the bowl with plastic wrap or a tight-fitting cover and refrigerate overnight for at least 18 hours.

Deflate. 2 hours before you want to bake the focaccia, take the bowl out of the fridge and uncover it. Using your hands deflate the dough slightly and transfer the dough to a buttered and oiled baking tray (9x13) or sheet pan.

Shape. Shape it loosely by grabbing each end and folding it over like you would a letter. Flip the dough over so the seams are on the bottom. Cover the tray with a tea towel and set aside for 1.5-2 hours.

Make Caramelized Onion. Set a non stick pan on medium heat and add 3 tbsp Butter. Once the butter has melted, add 4-5 White or yellow onions (thinly sliced), ¼ tsp Salt and ¼ tsp Black pepper. Keep stirring until the onions have softened (but not browned), about 4-6 minutes. Turn the heat down to low and continue to caramelize the onions for 30-40 minutes, or until the onions are soft and lightly browned. Add 1 tbsp Balsamic Vinegar, stir, and set aside to cool.

Dimple. Preheat your oven to 425F/220C. The dough should now have spread covering the surface of the baking tray. If not, you can help it stretch to the edges by carefully easing it to the corners. Drizzle more olive oil over the dough and start dimpling with your fingers, covering the entire surface. This creates valleys and mountains in the dough and you should also see air bubbles forming.

Dress. Nestle your caramelized onions, 1 cup Gruyere cheese (cubed) and 2 tsp Fresh thyme in the dough. Press the ingredients down.

Bake. Bake in the preheated oven for 20-25 minutes, until golden brown.