Preheat oven to 350F.
Heat a greased pan over medium heat on the stove. Add the chopped spinach. Cook, stirring occasionally, until the spinach is wilted and bright green. Set aside to cool.
Meanwhile, heat the cream cheese in a small saucepan on the stove over low heat for 1 minute. Once it has melted add mayonnaise, sour cream, grated parmesan and cheddar cheeses, artichoke hearts, Worcestershire sauce, mustard, lemon juice, minced garlic, black pepper, and half of the shredded mozzarella. Stir to combine.
When the spinach is cool, gather it into a ball in your hands and squeeze, getting rid of as much water as possible. Add the spinach to the stovetop mixture.
Scoop the dip into a large ramekin or your favourite appetizer dish. Smooth the top with a spatula. Sprinkle the remaining Keto Spinach Dip with shredded mozzarella.
Bake for 30 minutes until hot and bubbly. Serve warm with flat bread, chips or carrot and celery sticks.