Preheat and Prepare: First, preheat your oven to 180°C (160°C fan). Lightly grease a 1-litre ovenproof baking dish or a small cast-iron skillet.

Squeeze the Spinach: This is the crucial step for a thick, creamy dip. Place the thawed spinach in the centre of a clean tea towel or several layers of kitchen roll. Gather the edges and twist, wringing out as much liquid as humanly possible over the sink. You'll be surprised how much comes out. Set the dry spinach aside.

Create the Creamy Base: In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Use an electric hand mixer or a sturdy whisk to beat them together until the mixture is completely smooth and free of lumps. I find that letting the cream cheese soften properly for about 30 minutes at room temperature makes this step much easier.

Combine the Ingredients: Add the squeezed spinach, minced garlic, onion powder, nutmeg, salt, and pepper to the cream cheese mixture. Stir in about two-thirds of the mozzarella, Cheddar, and Parmesan cheese, reserving the rest for the topping.

Mix Thoroughly: Stir everything together until all the ingredients are evenly distributed. The mixture should be thick and cohesive.

Assemble the Dip: Spoon the spinach mixture into your prepared baking dish and spread it out into an even layer with the back of a spoon or a spatula.

Add the Topping: Sprinkle the remaining mozzarella, Cheddar, and Parmesan cheese evenly over the top of the dip.

Bake Until Bubbly: Place the dish in the preheated oven and bake for 20-25 minutes. You're looking for the top to be a beautiful golden brown and for the edges to be bubbling happily.

Rest and Serve: Carefully remove the dip from the oven and let it rest for at least 5-10 minutes before serving. This allows it to cool slightly and for the flavours to settle. Serve warm with your favourite dippers.