Rachael's A Burger To Love: Balsamic-Rosemary Cheese Burgers with Horseradish Sauce, Mushrooms and Onions

For the onions:

• 2 tablespoons butter
• 2 onions, chopped
• Salt and fine black or white pepper
• 1 bay leaf

For the mushrooms:

• 3 tablespoons extra-virgin olive oil (EVOO)
• 1 pound cremini mushrooms, sliced
• 2 tablespoons fresh thyme, chopped
• 4 large cloves garlic, chopped
• Salt and pepper
• ¼ cup sherry or ½ cup white wine
• Juice of 1/2 lemon

For the burgers:

• 8 slices meaty bacon
• 1½ pounds (80/20) ground beef
• 3 tablespoons grated onion
• Salt and pepper
• 2 tablespoons fresh rosemary, finely chopped
• 2 cloves garlic, grated or pasted
• 2 tablespoons Balsamic drizzle or aged Balsamic vinegar
• 2 tablespoons extra-virgin olive oil (EVOO)
• 8 slices fontina or mild provolone cheese
• 4 burger buns, split
• 4 slices beefsteak tomato

For the horseradish sauce:

• ½ cup sour cream
• ¼ cup aquafaba-based/chickpea mayo or mayonnaise
• 2 tablespoons horseradish
• 1 teaspoon black pepper
• Juice of ½ lemon
• ¼ cup finely chopped chives or scallions

Preheat oven to 375˚F.

For the onions, in a skillet over medium heat, melt butter, add onions and season with salt and pepper, add a bay leaf. Cook onions, low and slow, to light caramel color, 20-25 minutes. Add 1 cup water, and cook over low heat until liquid is completely absorbed, 10 minutes more.

Meanwhile, for the mushrooms, preheat a second skillet over medium-high heat, add EVOO, 3 turns of the pan, and add mushrooms to brown, 10-12 minutes. Add thyme, garlic, and salt and pepper, and cook 5 minutes more. Add sherry or wine, let it absorb completely, turn off the heat, then add lemon juice.

Arrange bacon on slotted pan or wire-rack lined baking sheet and bake until crisp, 12-15 minutes. Mix together ingredients for horseradish sauce.

For the burgers, preheat a large cast-iron griddle or skillet over medium-high heat. Place beef in bowl. Using a handheld grater, grate onion over bowl so meat collects juices. Season with salt, pepper and rosemary. Add garlic, Balsamic and EVOO, mix into meat, and form 4 patties thinner at center and thicker at edges for even cooking. Cook patties 8 minutes, turning occasionally, melt 2 slices cheese on each patty.

Assemble burgers: bun bottom, horseradish sauce, bacon, sliced tomato, burger patty, mushrooms, onions, bun top.