Preheat the oven to 176°C or 350°F
Heat the olive oil in a large (12-inch) sauté pan over medium heat.
Add the onion and celery and cook for 5 to 7 minutes, stirring occasionally, until the onion is translucent but not browned.
Set aside to cool slightly.
Place the beef, veal, pork, parsley, thyme, chives, eggs, milk, salt, and pepper in a large mixing bowl.
Put the panko in a food processor to obtain a finely ground breadcrumb mix.
Add the onion mixture and the panko to the meat mixture.
Gently toss the mixture together with your hands, making sure it’s combined but not compacted.
Place a piece of parchment paper on a sheet pan.
Pat the meat into a flat rectangle and then press the sides in until it forms a cylinder down the middle of the pan (this will ensure no air pockets).
Bake for 40 to 50 minutes or check the internal heat to be around 155°F to 160°F.
Remove from the oven and allow to rest for 10 minutes.
Slice and serve hot with the Garlic Sauce.