Preheat the oven to 375°F. In a mixing bowl, combine the ground beef, breadcrumbs, egg, 2 tablespoons of the herbs, salt, and pepper. Mix until just blended, then shape into a loaf on a baking sheet. Sprinkle the remaining tablespoon of herbs over the top and press lightly to help them stick.
Bake the meatloaf for 35 to 40 minutes until it reaches 160°F inside.
While the meatloaf bakes, bring the milk to a gentle simmer in a medium saucepan. Slowly whisk in the cornmeal and cook, stirring often, for about 10 minutes until thick. Stir in 2 tablespoons of butter and the Parmesan cheese, then remove from heat and cover to keep warm.
Heat the olive oil and remaining tablespoon of butter in a large skillet over medium heat. Add the minced garlic and cook for 30 seconds, then add the spinach. Sauté for 2 to 3 minutes until just wilted. Season lightly with salt if needed.
Slice the meatloaf and serve portions with a scoop of polenta and a side of the sautéed spinach.