Pour 325ml lukewarm water into a large bowl. Add the yeast and sugar and whisk to dissolve.

Leave to stand for 5 mins. It should get foamy, or at the very least, creamy. If it doesn’t, your yeast is likely dead and you’ll need to start over with fresher yeast.

Add the strong white bread flour and 10g fine sea salt and mix until a shaggy dough forms.

Turn the dough out onto a floured work surface. Knead until smooth, elastic and no longer sticky, around 5 mins.

Divide the dough into two and roll into balls.

Place each ball in a floured bowl, cover with a cloth and leave to prove in a warm place for 1 hour, or until doubled in size.

Meanwhile, finely chop the onion and garlic.

Heat a splash of olive oil in a saucepan set over a medium heat. Add the onion and cook until softened but not browned, 7 to 10 mins.

Add the garlic and cook for 1 minute, then add the crushed tomatoes and basil sprigs. Season with salt and pepper and stir to combine.

Reduce the heat to low and simmer for 30 mins, stirring occasionally. Adjust the seasoning to your liking and leave to cool.

Meanwhile, thinly slice the mozzarella and pick the basil leaves.

Punch down the dough to expel the air then turn it out onto a floured work surface and knead it for 1 minute to further deflate it.

Roll each dough ball into a ½ cm-thick rectangle. Spread with some of the marinara, leaving a 2cm border around the edge. Top with the deli meats, mozzarella slices and basil leaves.

Roll the dough up into a log and tuck in the ends to enclose the filling.

Place the two stromboli on two greaseproof paper-lined baking trays and leave to rise for 30 mins.

Heat your oven to 200°C / fan 180°C.

Beat the egg. Brush the stromboli with the egg wash, sprinkle with flaky salt and bake for 25 to 30 mins, or until well risen and golden brown.

Leave to cool for 10 minutes, then slice thickly and serve with any remaining marinara.