Preheat the oven to 350 degrees.
Chop the red onion and clean and slice the leek.
Get a sauce pan on the stove over medium heat.
Add the butter and the red onion to the pan and cook for about 7 minutes until tender.
Then add the leek and cook for another 2-3 minutes.
Next add the beef, panko, milk, egg, soy sauce, salt and pepper to a large bowl.
Add the onions and leek to the same bowl.
Next pull the prosciutto into smaller pieces and add to the same pan you just cooked the onions and leeks in, cook at medium heat.
Cook the prosciutto until it's browned (but not burned) and caramelized about 3 minutes.
Add the prosciutto to the bowl and mix together all the ingredients until well combined - I always use my hands, feel free to use a spoon!
Split the mixture into two halves and plop them onto a baking sheet.
Form them into two loaves and pop into the oven.
Cook for 45 minutes, remove and let cool for a few minutes, then serve with a dollop of creamy mashed potatoes and caramelized carrots. YUM.
