Preheat oven to 375°F.
Heat butter in a medium skillet over medium heat. When it foams, add onion and garlic, season with salt and freshly ground black pepper, and cook until onion and garlic are beginning to turn brown in color, about 6 minutes. Stir in flour and cook stirring constantly until no longer raw tasting, about 1 minute.
Sprinkle in 3/4 cup of the Parmesan, pour in cream, and stir to incorporate. Add artichoke hearts, sour cream, and 1/2 of the Gruyère and fontina and stir until cheese begins to melt.
Evenly spread the mixture in the skillet so it’s in a uniform layer and top with remaining Parmesan, Gruyère, Fontina and the panko. Bake until heated through, bubbling on the edges, and the cheese is melted, about 30 to 35 minutes. Let rest 5 minutes. Serve with Stonefire Naan for dunking.