Melt butter in a small pan and slowly cook the leeks and shallots until softened and caramelized.
Make the spring aioli by combining fresh chive, pesto, 1 Tbsp. of the caramelized leeks and shallots, a roasted garlic clove and mayonnaise in a small food processor. Pulse until combined and season to taste with salt and pepper. Chill until ready to use.
Grill the BUBBA burgers to your desired doneness; melt Swiss cheese and top with a heap of the remaining caramelized leeks and shallots during the final minute of cooking. Assemble the burger on a pretzel bun spread with spring aioli, and top with fresh arugula before serving.
Recipe by DomestikatedLife at https://domestikatedlife.com/2022/05/01/spring-burger-with-swiss-and-leeks/