Frozen fava beans work well in this recipe. If you cannot get fava beans, substitute edamame. If using fava beans, you will need to start with more than one cup of shelled beans to have one cup of peeled beans after cooking.
Cook fava beans or edamame till tender, approximately 3-4 minutes. Drain and shock in ice water.
If using fava beans, peel them.
Coarsely chop the cooked beans in a small food processor.
Remove half the beans and reserve.
Coarsely chop 1/2 ounce of arugula by hand. Reserve.
To the beans in the food processor, add 1/4 cup of olive oil, the remaining 1/2 ounce of arugula, mint leaves (if using), Pecorino Romano cheese, lemon zest, and lemon juice.
Process until almost smooth.
Combine puree with the coarsely chopped beans and arugula and mix by hand.
Adjust salt, pepper, and lemon juice. Refrigerate several hours, or overnight, to allow flavors to blend.
Return to room temperature before using.
To serve, toast slices of baguette. Drizzle one side of the toasted bread with extra-virgin olive oil. Rub the bread with the cut side of a garlic clove, distributing the oil.
Top each slice of bread with some of the bean mixture.