Follow these detailed steps to craft the perfect flatbread. We will break it down into three main stages: preparing the dough, caramelizing the onions, and finally, assembling and baking your masterpiece.

Part 1: Preparing the Flatbread Dough

This versatile dough is easy to make and provides the perfect canvas for our toppings.

1. Activate the Yeast: In the bowl of a stand mixer or a large mixing bowl, combine the warm water, instant yeast, and granulated sugar. Give it a gentle whisk and let it sit for 5-10 minutes. You’ll know the yeast is active when the mixture becomes foamy and smells fragrant. If it doesn’t foam, your yeast may be old or the water was too hot/cold; you’ll need to start over.
2. Mix the Dry Ingredients: In a separate medium bowl, whisk together the bread flour and kosher salt. This ensures the salt is evenly distributed and doesn’t come into direct contact with the yeast initially, which can inhibit its activity.
3. Combine and Knead (Stand Mixer Method): Attach the dough hook to your stand mixer. With the mixer on low speed, gradually add the flour mixture to the wet ingredients. Once combined, add the 2 tablespoons of olive oil. Increase the speed to medium-low and knead for 6-8 minutes. The dough should become smooth, elastic, and pull away from the sides of the bowl. It should be slightly tacky to the touch but not overly sticky.
4. Combine and Knead (By Hand): If you don’t have a stand mixer, add about half the flour to the yeast mixture and stir with a wooden spoon until combined. Add the remaining flour and olive oil, and mix until a shaggy dough forms. Turn the dough out onto a lightly floured surface. Knead for 10-12 minutes, adding a little extra flour to your hands and the surface as needed to prevent sticking. The dough is ready when it’s smooth, elastic, and springs back when you poke it gently.
5. First Rise (Proofing): Form the dough into a ball. Lightly grease the mixing bowl with olive oil and place the dough inside, turning it over once to coat the top. Cover the bowl with a clean kitchen towel or plastic wrap. Let it rise in a warm, draft-free place for 60-90 minutes, or until it has doubled in size.

Part 2: The Art of Caramelizing Onions

This is the most time-consuming part, but it’s where the magic happens. Patience is your most important ingredient here.

1. Prep the Onions: Peel the onions, cut them in half from pole to pole (root to stem), and then slice them thinly into half-moons.
2. Start the Sauté: In a large, heavy-bottomed skillet or Dutch oven, melt the butter and olive oil over medium-low heat. The combination of butter for flavor and oil for a higher smoke point is ideal.
3. Cook Low and Slow: Add the sliced onions to the pan, along with the 1 teaspoon of kosher salt and the black pepper. The salt will help draw moisture out of the onions. Stir to coat them in the fat. Let the onions cook slowly, stirring every 5-7 minutes. Do not rush this process by turning up the heat, as the onions will burn before they have a chance to sweeten and caramelize.
4. The Caramelization Process (30-45 minutes):
   • First 10 minutes: The onions will soften and become translucent.
   • Next 10-15 minutes: They will start to turn a pale, golden yellow and release a lot of their liquid. You might see some brown bits (fond) forming on the bottom of the pan – this is pure flavor!
   • Final 10-20 minutes: The onions will take on a deep amber or rich brown color and become incredibly soft and jam-like. Stir more frequently now to prevent burning. If the fond on the bottom of the pan looks like it’s getting too dark, deglaze the pan by adding a tablespoon of water and scraping the bits up with your wooden spoon.
5. Finish: Once the onions are a deep, rich brown and have a jammy consistency, remove them from the heat. Stir in the fresh thyme leaves, if using. Set aside to cool slightly.

Part 3: Assembling and Baking the Flatbread

Now it’s time to bring all the elements together.

1. Preheat Your Oven: Place a baking stone or a large, inverted baking sheet on the middle rack of your oven. Preheat the oven to 450°F (232°C). Preheating your baking surface is key to achieving a crispy bottom crust.
2. Divide and Shape the Dough: Once the dough has doubled in size, gently punch it down to release the air. Transfer it to a lightly floured surface and divide it into two equal pieces. Let the pieces rest for 5 minutes to allow the gluten to relax, which makes shaping easier.
3. Roll it Out: Working with one piece of dough at a time, gently stretch and roll it into a rustic, oblong or circular shape, about 1/4-inch thick. Place the shaped dough onto a piece of parchment paper.
4. Top the Flatbread: Brush the entire surface of the dough with a thin layer of extra virgin olive oil. This prevents the crust from getting soggy and adds flavor. Spread half of the cooled caramelized onions evenly over the dough, leaving a small ½-inch border around the edges. Sprinkle half of the crumbled feta cheese over the onions.
5. Bake to Perfection: Carefully slide the parchment paper with the flatbread onto your preheated baking stone or sheet. Bake for 12-15 minutes, or until the crust is a deep golden brown and the feta is slightly melted and toasted.
6. Repeat: While the first flatbread is baking, you can assemble the second one on another piece of parchment paper.
7. Garnish and Serve: Once baked, carefully remove the flatbread from the oven. Let it cool for a minute or two before drizzling with balsamic glaze. Slice and serve immediately for the best experience.