Mozzarella Mushroom Blended Burger with Caramelized Onions

There are few burger combinations as classic as mushrooms and mozzarella. Using the Blend and Extend technique, these fresh mozzarella blended mushroom burgers with caramelized onions are a new take on an old favourite.
Recipe and photo by James of From James to Jamie.
Prep Time: 15 minutes | Cook Time: 35 minutes
Ingredients
200 g. cremini mushrooms
400 g. extra lean ground beef
½ tsp. salt, dash of pepper
medium yellow onion, halved and sliced
1 tbsp. butter
1 tbsp. balsamic vinegar
Extra virgin olive oil
4 brioche buns
4-8 slices fresh mozzarella
Mayonnaise
BBQ sauce (optional)
400 g. extra lean ground beef
½ tsp. salt, dash of pepper
medium yellow onion, halved and sliced
1 tbsp. butter
1 tbsp. balsamic vinegar
Extra virgin olive oil
4 brioche buns
4-8 slices fresh mozzarella
Mayonnaise
BBQ sauce (optional)
Method
1. Blend/pulse your mushrooms until fine in a food processor.
2. Cook the mushrooms on a griddle (or in a large frying pan) over medium heat for about 4-5 minutes, stirring often. Set aside to cool.
3. Give the griddle a quick wipe-down, turn it down to low-medium, and toss on your sliced onions along with the butter. Cook for about 15-20 minutes, stirring often, until soft and golden.
3. While the onions are cooking and once the mushrooms have cooled, combine the mushrooms together with your ground beef in a prep bowl. Stir until well-combined and form into four patties. Place the patties on a plate, cover, and place in the fridge.
4. Once the onions are the right texture and colour, add the balsamic vinegar and cook another two minutes, stirring often. Remove from the griddle and set aside.
5. Wipe down your griddle, turn it back up to medium, then add a small lug of oil and spread it around.
6. Combine together your salt and pepper in a small prep bowl, then sprinkle roughly half of your seasoning on the tops of your burgers. Place the burgers on the griddle with the seasoned side facing down.
7. After about 4 minutes, season the tops of the burgers with the other half of your salt/pepper mix, then flip. Cook an additional 3-5 minutes until no pink remains.
8. Construct your burgers by applying mayo to both sides of your buns, then adding the patties and topping with 1-2 slices of fresh mozzarella and your caramelized onions.
2. Cook the mushrooms on a griddle (or in a large frying pan) over medium heat for about 4-5 minutes, stirring often. Set aside to cool.
3. Give the griddle a quick wipe-down, turn it down to low-medium, and toss on your sliced onions along with the butter. Cook for about 15-20 minutes, stirring often, until soft and golden.
3. While the onions are cooking and once the mushrooms have cooled, combine the mushrooms together with your ground beef in a prep bowl. Stir until well-combined and form into four patties. Place the patties on a plate, cover, and place in the fridge.
4. Once the onions are the right texture and colour, add the balsamic vinegar and cook another two minutes, stirring often. Remove from the griddle and set aside.
5. Wipe down your griddle, turn it back up to medium, then add a small lug of oil and spread it around.
6. Combine together your salt and pepper in a small prep bowl, then sprinkle roughly half of your seasoning on the tops of your burgers. Place the burgers on the griddle with the seasoned side facing down.
7. After about 4 minutes, season the tops of the burgers with the other half of your salt/pepper mix, then flip. Cook an additional 3-5 minutes until no pink remains.
8. Construct your burgers by applying mayo to both sides of your buns, then adding the patties and topping with 1-2 slices of fresh mozzarella and your caramelized onions.