Heat a large skillet over medium-low heat, then add the oil to warm through. Once warm, add the onions and sauté, stirring occasionally for about 15 minutes. Lower the heat to low and add a pinch of salt and continue cooking the onions, adding a splash of water as needed to prevent the onions from sticking or burning. Cook until they become a deeper brown color (this can vary depending on your patience, so generally I’ll cook for an extra 15-25 minutes, but if you take longer to fully caramelize them the sweeter the onions will get).
Add in 2 cloves of minced garlic and sauté with the onions until fragrant, about 1-2 minutes. Stir in the balsamic vinegar and maple syrup, and fold into the onions. Once absorbed, remove the pan from heat.
To a medium mixing bowl, add the chickpeas and use a fork to mash them as much as you like (I generally mash about ⅔ of the chickpeas). Add the yogurt, mayo, nutritional yeast, the remaining clove of minced garlic, lemon zest and juice, chives, half the caramelized onions, and a generous pinch of salt. Stir the mixture together until well combined then adjust seasonings to taste.
To assemble, toast your bread, spread with mustard or cream cheese, layer on the lettuce, the chickpea salad and top with more caramelized onions as desired then enjoy.