Boil the potatoes with their skins on – after having washed them thoroughly – in plenty of slightly salted water, for about 20 minutes; try pricking them with a fork, if it goes in easily, they’re cooked. Strain them and peel them while still hot, the skins will come off easier. Top and tail the beans, wash them and then cook them in plenty of boiling, salted water. When they’re cooked, strain and leave them to cool down. In the meanwhile, put the chickpea flour in a large bowl with some salt and the olive oil. Very slowly pour in the water and stir with a whisk until you have a smooth, fairly liquid batter (use a spoon to remove any froth that may form on the surface). Add the pesto and stir again. Cut the potatoes and green beans into small pieces, set a few aside as a garnish, put the rest into the bowl with the batter and stir well. Pour the mixture into the tartlet tins which you have previously greased well with olive oil. Cook in a preheated oven, at 200 °C, for 30-35 minutes; take the flans out of the oven and, when they are lukewarm, remove them from the tins. Garnish them with the pieces of potato and beans that you set aside and... they’re ready to serve!