Add the olive oil, garlic, and onion to a skillet. Cook this over medium heat 5-10 minutes, until the onion is softened.
Add the artichoke hearts, frozen spinach, cream cheese, sour cream, mayo, and parmesan cheese to a sauce pan or dutch oven and stir the mixture over medium heat until melted and creamy.
Stir the garlic and onion into the dip mixture once it is done cooking.
Salt the dip to taste (I used ½ teaspoon of salt).
Transfer the spinach artichoke dip mixture to a small greased baking dish.
Top the dip with the mozzarella cheese.
Bake the spinach artichoke dip at 375 degrees for 15-20 minutes, until hot and bubbly.
Optional: broil the dip for 1-2 minutes at the end to get the top browned. Watch closely to avoid burning.
Serve with chips, crackers, or baguette slices.