Bring the potatoes to the boil in a large pan of water. Simmer for 15 minutes, then drain in a colander and set aside for 20 minutes to cool.
Sift the flours into a large bowl. Add yeast, salt, sugar and basil, and mix. Mash the potatoes with the olive oil, add to the flour mixture and mix well.
Gradually add warm water, stirring constantly with a wooden spoon. Once the mixture is well combined, transfer it onto a clean work surface and knead for around 10 minutes. Place into a bowl, cover with a cloth and leave in a warm place for an hour.
Grease a 23cm x 23cm baking tin. Place the dough into the baking tin and spread it out using your fingers to fit the tin. Tuck some tomatoes into the dough at regular intervals. Cover the tin with a cloth and leave to prove for another 30minutes.
Preheat the oven to 220ºC. Bake your focaccia for 30 minutes until golden-brown.
Serve with cress, salads or simply finished with a tiny drizzle of extra vergin olive oil.
GF – make sure the ingredient doesn’t contain traces of gluten!