Combine the sourdough starter and 350g lukewarm water in a large bowl, stirring until dissolved

Add flour, salt and Marmite. Mix until a shaggy dough forms

Knead for 8–10 minutes until the dough becomes smooth and elastic, adding the olive oil as you knead

Cover the dough with a damp cloth or plastic wrap and let it rise at room temp for 8–10 hours, or until doubled in size

Preheat the oven to 180°C

Toss the butternut squash with olive oil, smoked paprika, salt and pepper

Spread the squash on a baking tray and roast for 15–20 minutes until slightly tender but not fully cooked. Set aside to cool

For the crunchy topping, heat the olive oil in a small pan over medium heat. Add the sage leaves and fry until crisp, about 1–2 minutes. Remove the leaves from the oil and drain them on paper towels

Mix the crispy sage leaves with grated Parmesan

Generously oil a 9 × 13-inch (23 × 33 cm) baking pan. Stretch the risen dough to fit the pan evenly

Cover and let the dough rise for another 1 hour until puffy

Lay the roasted butternut squash cubes over the dough

Sprinkle the sage and Parmesan crunch on top

Use your fingers to press dimples into the dough, pushing the toppings slightly into the dough

Bake the focaccia for 30–35 minutes, or until the edges are golden and the top is slightly crisp

Let the focaccia cool in the pan for 10 minutes before transferring it to a wire rack

Slice into pieces and serve warm or at room temperature