In a large bowl combine beef and pork, beaten egg, basil and oregano, breadcrumbs and salt, mix well and shape into 20 meatballs. (Alternatively you can use store-bought meatballs and skip this step.)
(Baking method) Place meatballs on a parchment paper lined rimmed baking sheet and bake in the preheated oven at 200C/400F for 10 minutes. (The meatballs will not be baked all the way through.)
OR....(Frying method) Heat olive oil in a large frying pan and brown the meatballs over medium heat but don't cook all the way through. Remove from the pan and set aside.
To the same pan add 1 tbsp of olive oil, chopped garlic and basil and cook briefly for 1 minute, then add canned tomatoes previously processed in a blender until smooth or leave chunky for extra texture if desired. Then add 3 tbsp of basil pesto and salt, bring to a boil, then lower the heat and let it simmer for approximately 5-7 minutes.
Return the meatballs to the pan with the sauce, add arugula and mix, then scatter mini mozzarella balls, halved cherry tomatoes and basil leaves on top.
Bake in the preheated oven for 30 minutes until the sauce is bubbly and mozzarella is melted and golden.