Heat your grill to high. No grill? Just set your oven to its highest setting.
Trim the beans. Scatter them on a baking tray. Toss with 1 tsp oil. Season well. Grill (or roast) for 3-4 mins till just tender and starting to char.
Grate the garlic and the lemon zest into a small bowl. Add 2 tbsp tahini and 2 tbsp lemon juice. Stir in 1 tbsp oil and 1 tbsp water. Season to taste.
Drain and rinse the chickpeas. Tip into a bowl. Use a veg peeler to make thin carrot ribbons. Add to the beans with half the dressing. Toss to mix.
Thinly slice the spring onions. Tip into a separate bowl. Squeeze over the remaining lemon juice. Toss to mix.
Spoon the salad onto two plates. Scatter over the lemony spring onions. Drizzle or dollop over the remaining dressing.