Melt butter over medium heat. Once fully melted, turn the flame down low and whisk in the flour.  Add the heavy cream ¼ cup at a time until the mixture is smooth and thick.

Stir in the worcestershire sauce, dijon mustard and black pepper, then add the cream cheese. Keep stirring until the cream cheese is fully melted. You can turn the flame up slightly for this step.

Add a few handfuls of spinach at a time rather than adding it all at once. As the spinach wilts, it will be easier to fit more in the pan. Mix the spinach until its's evenly coated.

Turn flame really low and stir in the artichoke and crab meat. Stir carefully until the crab and artichokes are covered. Try not to break up the lumps of crab meat or the artichokes.

Turn the flame off and stir in the parmesan and mozzarella cheeses. The heat from the hot dip will melt the cheese. 

Transfer the crab and spinach dip to a baking dish or leave it in the cast iron skillet. Place under the broiler for 5-6 minutes, or just until the cheese is slightly browned on top.

Let the dip cool just slightly and serve with crostini, crackers, warm bread or in a bread bowl!