Make fava salad: In a bowl, coarsely mash fava beans with a pastry blender. Stir in oil, lemon juice, and salt. Set aside.
Make egg salad: Peel and slice eggs; set aside. Using a mortar and pestle, coarsely grind garlic, coriander seeds, chile, caraway seeds, and salt to make tabil. Stir in mayonnaise, mashing mixture a bit.
Generously smear one side of toasts with tabil mayonnaise. Arrange a layer of eggs on top, then spoon fava salad over eggs. Scatter chopped cilantro over sandwiches and garnish with cilantro leaves. Serve sandwiches open-face and eat with a knife and fork.
*Find in the spice aisle at well-stocked supermarkets, Latino markets, and americanspice.com.
How to Double-Shell Favas: Makes 2 cups 30 minutes Tear open 3 lbs. fava pods*. Add beans from pods to a pot of boiling salted water and return to a boil. Cook just until beans are tender beneath skin (slit to check), 2 minutes. Drain; rinse with cold water. Peel leathery skin by tearing beans open at rounded ends and popping out beans. *Find at well-stocked grocery stores and farmers' markets. Make ahead: All but the final peeling, up to 1 day, chilled.