Make the chickpea salad: In a food processor, combine the chickpeas, tahini, Dijon mustard, garlic, capers, green onions, cilantro, lemon juice, and pinches of salt and pepper. Pulse until combined, but do not puree. Season to taste.
Blanch the green beans. Bring a small pot of salted water to a boil and place a bowl of ice water nearby. Drop the green beans into the boiling water for 1½ minutes, then scoop into the ice water to stop the cooking process. Once cool, drain, pat dry, and chop into 1-inch pieces.
Assemble the sandwiches: Spread the chickpea salad on one side of the baguette. Press the chopped green beans into the chickpea salad and top with the olives and red onion slices. Spread of layer of mayo on the other half of the baguette and top with the sliced cucumbers, radishes, and basil. Season with salt and pepper, to taste. Press together, slice, and enjoy!