How to Make It
Combine the cream cheese and mayonnaise in a large bowl and stir until smooth. Add the artichokes, spinach, Fontina, Parmesan, and garlic powder. Season to taste with salt and pepper.
Heat oven to 375°. Lay one sheet of phyllo on a large, flat surface. (Keep unused sheets of phyllo covered with a lightly moistened kitchen towel to prevent drying.) Brush the first sheet liberally with butter and top with another sheet of dough. Repeat the layering with three more sheets of dough, ending with butter.
Use a sharp knife to cut the dough into 20 squares, approximately 2½-inches each. Working one square at a time, crimp the edges and fit the dough into the cavities of a mini-muffin pan, making a tulip shape. Fill each cup with 2 tablespoons of the spinach-artichoke mixture.
Using a second muffin pan, repeat the process again with the remaining dough and filling. (You should have about 40 phyllo cups, total.)
Bake the phyllo cups until they are golden brown and the filling has puffed, rotating the pan halfway through, 15 to 20 minutes. Let phyllo cups cool 5 minutes before removing them from the pans. Serve warm or at room temperature.