Preheat the oven to 175 degrees F.
Halve all but 2 of the artichoke hearts and grill the rest over medium-high heat on an oiled grill (a grill pan may be substituted) until lightly charred and warmed through. Keep warm in the oven while preparing the spinach and artichoke dip.
In a large skillet, heat the olive oil over medium-high heat. Saute the onions until tender and translucent, about 3 minutes. Add the spinach and cook until wilted and all the moisture in the pan has evaporated, about 3 minutes. Chop the reserved whole artichoke hearts and add, along with the Greek yogurt, mozzarella and Parmesan. Cook until cheese has melted. Add the basil and nutmeg, season with salt and pepper, and serve on top of grilled artichoke hearts.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.