Preheat oven to 425 degrees. Place sliced sourdough on a foil covered baking sheet and brush the bread with a small amount of olive oil. Bake 8-10 minutes until lightly toasted. Remove from oven and cool.
Prepare fava beans and place in bowl. With a fork, smash about 1/2 of them and leave the rest whole, halved or in pieces. Add preserved lemon, lemon juice, mint, 1 T olive oil, pinch of salt and pepper and mix together. Adjust the olive oil and lemon juice to your desired taste.
To serve, spread ricotta cheese on each crostini and spoon on the desired amount of fava bean spread. Serve immediately. Serves 4-6.