In a 16 ounce Mason jar, add your apple and onion slices. Fill until just covered with water. Add the rest of ingredients. Let it sit in the fridge for a few hours or up to two days.

In a food processor, blend the mayo, garlic, walnuts, and salt until smooth. Thin out with water until it reaches your desired consistency. 

In a food processor, grind the mushrooms until very fine. Sauté in olive oil with salt and pepper. It will end up looking like browned ground meat. Set aside in a bowl to cool.

In the same food processor, blend the sage leaves, mint leaves, and garlic until it resembles a paste. Mix this paste into your ground lamb along with salt and pepper. Add the cooled mushrooms to the mixture.

Form round patties from the mixture and cook for a few minutes a side on an oiled hot cast iron pan or grill.

Shmear a toasted challah bun or bun of your choice with garlic walnut aioli. Top with a lamb burger and pickled apples and onions. If you desire an added crunch, add some kale, as well.