Fry K&N’s Burger Patties as per instructions on pack.

In a pan, heat oil and sauté onions and mushrooms for 1 minute until translucent.

Place a bread slice, spread mayonnaise and top it with cheddar cheese slice.

Add sautéed onions and mushrooms and place Burger Patty.

Top it with cheddar cheese slice and place bread slice on top. Spread butter generously on both sides of the sandwich.

Heat a grill pan and toast the other side of the bread for a minute.

When done, cut from the middle. Serve warm.