Mushroom Swiss smash burger

Pop the stems out of the cremini mushrooms and slice them. Do not wash off the dirt; wipe it off with a towel, since washed mushrooms soak up water.

Cut the onion in half through the poles, trim both ends, peel, and slice.

Oil the flat top. Cook the onions on one side and the mushrooms on the other, breaking the slices up, until softened and the mushrooms go shiny as their water comes out.

Combine the onions and mushrooms. Add a splash of Worcestershire, then vermouth, season with BFF, and finish with butter so they turn silky. Take them off the heat.

Oil the flat top, put down one-third-pound beef portions and smash them thin. Season one side with BFF and add a little Worcestershire.

Spread mayo on the cut sides of the pretzel buns and grill them on the flat top to get colour.

Flip the patties, put baby Swiss on top, and cover to melt. High heat, only a couple of minutes in all.

Return the mushrooms and onions to the flat top for a few seconds to reheat, and add a squeeze of garlic paste.

Build: mayo on the bottom bun, two patties, then the mushroom and onion mixture, then the top bun.