Thaw the frozen spinach completely (microwave or overnight in fridge). Place the spinach into a clean kitchen towel or several layers of paper towels and squeeze firmly to remove as much water as possible. Finely chop if pieces are large.

Prep artichokes and garlic

Drain the canned artichoke hearts well, pat dry with paper towels, and chop into small bite-sized pieces. Mince the garlic cloves and measure out cheeses and dairy so they're ready to use.

Mixing the dip

Preheat the oven to 375°F (190°C). In a medium mixing bowl, add the softened cream cheese. Use a rubber spatula or electric hand mixer on low to beat cream cheese until smooth.

Add sour cream and mayonnaise to the cream cheese and mix until combined and creamy, scraping down the sides of the bowl.

Stir in the grated Parmesan, shredded mozzarella, and shredded cheddar (if using) until evenly distributed.

Add the squeezed spinach, chopped artichoke hearts, and minced garlic to the cheese mixture. Fold gently to combine so the spinach and artichokes remain distributed throughout the mixture.

Season the mixture with lemon juice, Worcestershire sauce, salt, black pepper, and red pepper flakes (if using). Taste a small amount and adjust salt/pepper or lemon to preference.

Baking & finishing

Transfer the dip into a medium ovenproof baking dish (about 9-inch round or equivalent) and smooth the top with a spatula. Sprinkle the extra 1/2 cup shredded mozzarella evenly over the top, then dust with the tablespoon of grated Parmesan.

Bake in the preheated oven for 18–22 minutes, until the dip is hot and bubbling and the top is golden in spots. For a more deeply browned top, finish under the broiler for 1–2 minutes—watch closely to avoid burning.

Remove from oven and let rest 5 minutes. Sprinkle chopped fresh parsley over the top and place lemon wedges alongside if using.

Serve

Serve the warm dip with tortilla chips or pita chips. Scoop generously and use chips to pick up the dip. Provide extra napkins; dip is best eaten hot.