Put the oil into a large saute pan for which you have a lid and place on a medium heat. Add the shallots, garlic, beans, tomatoes, dried oregano, chilli flakes, 1 tbsp of the lemon juice, 3/4 tsp salt and a good grind of pepper.
Stir to combine and cook , covered, for 35-40 minutes, stirring from time to time, until the beans have really softened and the shallots have started to catch and caramelise in places. Remove from the heat and add the fresh oregano, basil and the remaining 1/2 tbsp lemon. Stir to combine and set aside.
Combine the feta and mascarpone in a small bowl and mash together with a fork to a rough curd like texture. Set aside.
When ready to serve divide the feta and mascarpone between the toast and smear it all over using the back of a spoon. Arrange the beans on top, together with their oily juices. Scatter over the reserved oregano and basil leaves and serve.