Place a small nonstick skillet over medium heat and add 1 tablespoon of the oil. Add the sliced leek and 1/4 teaspoon of the salt and cook, stirring occasionally, until the leek is softened, about 3 to 4 minutes; reduce heat if it starts to brown. Add the minced garlic and stir for about 1 minute more. Remove the pan from heat and transfer the mixture to a large bowl to cool.

Wipe the skillet clean, return to medium-low, and toast the pine nuts, shaking the pan or stirring frequently, until fragrant and lightly golden—watch closely to prevent burning. Add the toasted pine nuts to the cooled leek mixture.

Put the drained chickpeas in a food processor and pulse until they form coarse, crumb-like pieces with some texture remaining (avoid pureeing). Transfer the processed chickpeas to the bowl with the leek, garlic, and pine nuts.

Add the egg, lemon zest, lemon juice, Dijon mustard, breadcrumbs, and the remaining 1/4 teaspoon salt to the chickpea mixture. Stir until everything is evenly combined and the mixture holds together when pressed.

Portion the mixture into 7 to 8 cakes using a small ice cream scoop or a 1/4-cup measure. Wet your hands lightly and press each portion into a firm, compact patty.

Return the skillet to medium heat and add the remaining 2 tablespoons olive oil. When the oil is hot, add the chickpea cakes and cook until the bottoms are golden and crisp, about 3 to 4 minutes. Flip and cook an additional 2 to 3 minutes until the second side is browned and the cakes are cooked through. Transfer to a plate lined with paper towels if desired and serve with the yogurt sauce.

In a small bowl, combine the Greek yogurt, minced garlic, 1/8 teaspoon salt, 1 teaspoon lemon juice, and 2 teaspoons olive oil. Whisk until smooth and taste; adjust seasoning with salt and pepper as needed. Serve chilled or at room temperature alongside the chickpea cakes.