1. Make the Dough:

In a large bowl, combine 350g room temperature water and whisk in 100g of active sourdough starter until mostly combined.

Add 500g bread flour on top of the mixture and sprinkle 12g salt over the flour.

Using a Danish dough whisk, spatula, or spoon, mix until a shaggy dough forms. Knead the dough with your hands until all the dry bits are incorporated.

Cover the bowl and set aside for 60 minutes.

2. Stretch and Fold:

Using damp hands, gently stretch the dough until the flap is long enough to fold over itself. Repeat this fold around the dough for a set of stretch and folds (4 times total).

Cover the bowl and let the dough rest for another 60 minutes. Repeat this stretching and folding process once more followed by another 60-minute rest.

3. Caramelize the Onions:

Slice the onion and add it to a heavy skillet with 2 tablespoons of butter.

Heat over medium-low heat, stirring frequently, until the onions are golden-brown, sweet, and fragrant. Remove from heat and let them cool in the fridge.

4. Laminate the Dough:

Lightly flour a work surface and turn the dough out onto it. Press and stretch it into a rectangle shape. If the dough resists, let it rest for a few minutes.

Spread about half of the caramelized onions (120g) over the top two-thirds of the dough, followed by 80g shredded Gouda cheese.

Fold the bottom third of the dough over the filling, then fold the left and right edges inward to seal. Spread the remaining onions and cheese across the remaining dough before folding it down to form a tidy package.

Transfer the dough to a large bowl and cover. Let it bulk ferment for 2 hours.

5. Pre-Shape and Shape the Dough:

After bulk fermentation, check that the dough has risen and is domed with visible bubbles. If it’s flat, let it ferment a bit longer.

Transfer the dough to a lightly floured surface, and gently press and stretch it into a large rectangle.

Fold up the bottom third of the dough, then fold the sides inward like folding a letter. Roll from the bottom to the top, forming a log.

Cover with a kitchen towel and rest for 30 minutes.

After resting, flip the dough over, clasp the ends towards the center, and press the dough together. Rotate it 90 degrees and clasp again to form a batard shape.

Dust the dough with rice flour and place it seam-side up into a banneton.

6. Prove and Cold Retard:

Let the dough prove in the banneton for 2-3 hours in a warm place. After proving, cover it and refrigerate for up to 3 days for better flavor. If baking right away, proceed to the next step.

7. Bake:

Preheat your oven to 450°F (230°C), placing a Dutch oven or cloche inside to heat.

Once preheated, invert the dough onto a piece of parchment paper. Score the dough using a sharp knife, lame, or razor blade.

Carefully place the dough into the hot Dutch oven using the parchment as a sling. Cover and bake for 30 minutes.

Uncover and continue baking for another 10-15 minutes, until the crust is golden brown and the internal temperature reaches 205–210°F (96-99°C).

8. Cool:

Remove the bread from the oven and transfer it to a wire rack to cool completely. Allow it to cool for at least 2 hours before slicing to preserve the crumb structure.