Clean the squid tubes and set aside; finely chop the tentacles.
Soak breadcrumbs in milk for 5 minutes then squeeze out excess moisture.
In a bowl, combine chopped tentacles, soaked breadcrumbs, egg, minced garlic, shallot, and parsley; season with salt and pepper.
Carefully stuff each squid tube with the mixture using a small spoon or piping bag, leaving 1cm at the top to secure with a toothpick.
Heat olive oil in a pan and sear the stuffed squids for 2 minutes per side until lightly browned.
Arrange the squids in a buttered baking dish in a single layer.
Pour the tomato passata evenly over the squids and sprinkle with the grated cheese.
Bake in a preheated oven at 200°C (390°F) for 25 to 30 minutes until the sauce is bubbling and the cheese is gratinéed.