In a large bowl, tear the toasted potato bread cubes into small pieces and pour the half-and-half over them. Let soak for 2 minutes. Add the ground turkey, eggs, grated onion, dried sage, nutmeg, salt, and pepper. Mix with your hands or a fork until just combined — do not overwork or the meatballs will be dense.

Preheat the oven to 400°F / 200°C (205°C fan-forced). Grease a rimmed baking sheet with melted butter.

Using a tablespoon or small cookie scoop, form the mixture into meatballs (you should get about 24). Place them on the prepared baking sheet with space between each.

Bake for 20 minutes, basting with melted butter halfway through, until the outsides are lightly browned and firm. Transfer the meatballs into the simmering sauce.

In a large saucepan or Dutch oven, combine the passata, cranberry sauce, lemon juice, Worcestershire sauce, prepared horseradish, salt, and pepper. Stir to combine.

Bring to a gentle simmer over medium heat and cook for 20 minutes, stirring occasionally, until the cranberry sauce has fully dissolved and the flavours have melded.

Add the baked meatballs to the sauce. Reduce the heat to low, cover, and simmer for 30 minutes, stirring gently every 10 minutes. The meatballs are done when they reach an internal temperature of 165°F / 74°C.

Split the rolls and toast them under the grill (broiler) for 1-2 minutes until lightly golden. Spoon 3-4 meatballs and a generous ladle of sauce onto each roll. Top with a slice of cheese — horseradish cheddar, Swiss, or mild provolone all work well — and return to the grill for 1 minute until the cheese melts. Serve immediately.