If using fresh spinach: heat a large skillet over medium, add 1 tsp olive oil (optional) and the spinach, stirring until wilted, about 2–3 minutes. Transfer to a bowl, let cool slightly, then squeeze out excess moisture in a clean kitchen towel or cheesecloth. Chop roughly. If using frozen spinach: thaw fully and press out all moisture until dry, then chop if needed.

Sauté aromatics

In the same skillet, melt the unsalted butter over medium heat. Add the finely diced onion and cook until soft and translucent, about 4–5 minutes. Add the minced garlic and cook 30–45 seconds until fragrant. Remove from heat and let cool slightly.

Mix Dip

Preheat the oven to 375°F (190°C). Lightly grease a 1.5-quart baking dish or an oven-safe skillet (9-inch) with butter or nonstick spray.

In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Beat with a whisk or rubber spatula until smooth and creamy.

Stir in the cooked and drained spinach, sautéed onions and garlic (cooled), grated Parmesan, shredded Gruyère (or cheddar), the egg, Dijon mustard, Worcestershire sauce, hot sauce (if using), lemon zest and juice. Mix until evenly incorporated.

Gently fold in the lump crab meat, taking care to keep some chunks intact. Season the mixture with Old Bay seasoning, kosher salt, and freshly ground black pepper. Taste and adjust salt, pepper, or hot sauce as desired.

Bake & Finish

Spoon the dip into the prepared baking dish, smoothing the top. Sprinkle the optional shredded mozzarella evenly over the surface for a golden top.

Place the dish on a middle oven rack and bake at 375°F (190°C) for 20–25 minutes, until the dip is bubbling around the edges and the cheese is melted and lightly browned on top. If you prefer a deeper brown, broil for 1–2 minutes, watching carefully to prevent burning.

Remove from oven and let rest 5 minutes. Sprinkle chopped fresh parsley over the top and serve warm with toasted baguette slices or crackers and lemon wedges.