1. To make the starter, mix the flour and yeast together in a large bowl. Using a wooden spoon, gradually stir in the water to make a smooth batter. Cover with plastic wrap. Let stand in the kitchen (not necessarily in a warm place) for 2 days, stirring daily. The finished starter will look separated and have a sharp aroma.

2. For the bread, mix the flour, yeast, sugar, fennel, and salt together in a large bowl. Make a well in the center. Stir the starter well. Add ¼ cup of the starter and the water to the flour mixture.

3. Stir until the dough comes together, adding a little more water if needed. Knead on a lightly floured work surface for 8–10 minutes, until the dough is smooth and elastic. Shape into a ball. Transfer to a clean bowl and cover with plastic wrap. Let stand in a warm place until doubled in volume.

4. Oil a large baking sheet. Punch down the dough and knead briefly on a lightly floured surface. Shape into a ball and flatten the top. Transfer to the baking sheet. Cover with plastic wrap and let stand in a warm place until doubled.

5. Preheat the oven to 425°F (220°C). Lightly dust the loaf with flour then, using a sharp knife, slash the top in a diamond pattern. Bake for 15 minutes. Lower the oven temperature to 375°F (190°C) and bake for 20–25 minutes, or until the bread sounds hollow when tapped underneath. Transfer to a wire rack and let cool.

Variation:

German Sourdough Bread (Bauernbrot): Replace 2 cups of the bread flour in the dough with rye flour.