4 hamburger patties (I used Wahlburgers)
4 slices gruyere cheese
Salt & pepper to taste
8 Tbsp butter (2 & 6 divided) + more for spreading on buns
6 onions, sliced
1 Tbsp olive oil
4 pretzel buns
2 cups arugula
Optional: 2 sprigs fresh rosemary, garlic aioli
In a large pot, heat 6 Tbsp butter and 1 Tbsp olive oil.When melted and hot, add sliced onions and stir.
Stir occasionally for about 30-45 minutes on medium heat, adding salt & pepper to taste about halfway through, until caramelized.
When the onions are almost done, heat 2 Tbsp butter in a large pan.Rub each burger patty all over with Milford Spice Company’s Prime Rib. Add salt & pepper to taste if you like.
Cook burgers, about 4-5 minutes on each side.Add fresh rosemary sprigs to the butter if you like.
After flipping the burger, add a slice of gruyere on top for the remainder 4-5 minutes until melted.
Spread butter on the insides of pretzel buns and toast in a pan, butter side down, for about 5 minutes until toasted golden brown.
When everything is done cooking, place some garlic aioli on the bottom half of the pretzel bun if you choose, add arugula, burger topped with melted gruyere, and top with caramelized onion and the top of the pretzel bun.