Bring a large pot of salted water to a boil. Add the 6 cups packed fresh spinach and blanch for 30–45 seconds until wilted. Immediately transfer spinach to an ice bath to stop cooking. Squeeze out as much liquid as possible using clean hands or a cheesecloth; finely chop the spinach and set aside. (If you prefer, you can sauté the spinach in 1 teaspoon olive oil for 1–2 minutes until wilted, then cool and chop.)

Drain the frozen spinach

Ensure the thawed frozen chopped spinach is well drained: press in a fine-mesh sieve or squeeze in a clean towel to remove excess water. Measure 1 cup drained and add to the chopped fresh spinach.

Prepare artichokes

Drain the canned artichoke hearts and pat dry. Chop coarsely until you have 1 cup. Pat again if very wet to avoid a watery dip.

Soften and combine base cheeses

In a large mixing bowl, combine the softened cream cheese (8 oz) with 1 cup ricotta. Beat with a wooden spoon or electric mixer on low until smooth and lump-free.

Add cheeses and aromatics

Fold in the shredded mozzarella (1 cup), shredded Monterey Jack (1 cup), and grated Parmesan (1 cup) into the cream cheese mixture. Add minced garlic (3 cloves), mayonnaise (1 tbs), lemon juice (1 tsp), Kosher salt (1 tsp), black pepper (1 tsp) and red pepper flakes (1 tsp). Mix until evenly distributed.

Combine spinach and artichoke with cheese

Fold the chopped fresh and drained frozen spinach and chopped artichoke hearts into the cheese mixture until evenly combined. Taste and adjust seasoning with additional salt, pepper, or lemon juice if desired.

Finish and transfer to baking dish

Preheat oven to 375°F (190°C). Transfer the mixture to a 9-inch (or similar) ovenproof baking dish, spreading into an even layer. Drizzle 1 tablespoon olive oil over the top and sprinkle a light dusting of extra grated Parmesan (if desired) for a browned top.

Bake

Bake in the preheated oven for 20–25 minutes until the dip is bubbly and the top is lightly golden. For a more browned crust, place under the broiler for 1–2 minutes, watching carefully to avoid burning.

Rest and garnish

Remove from oven and let rest for 5 minutes. Sprinkle chopped fresh parsley (reserve a little for flatbread garnish) over the top before serving.

Croustades & Grilled Flatbread

Prepare baguette slices (croustades)

Slice the baguette on a diagonal into 1/3-inch (approximately) slices to yield crispier rounds. Arrange slices on a baking sheet.

Brush and bake baguette

Mix melted butter (2 tbs) with the minced garlic clove (for brushing). Brush each baguette slice lightly on one side. Bake in the oven at 375°F (190°C) alongside the dip for 8–10 minutes, or until edges are golden and crisp. Flip and brush the other side half way through if needed. Alternatively, grill slices on medium heat for 1–2 minutes per side.

Prepare flatbread

Brush each flatbread lightly with olive oil (1 tbs total) and sprinkle 1/4 teaspoon salt over both. Heat a grill pan or outdoor grill to medium-high.

Grill flatbread

Grill each flatbread 1–2 minutes per side, until lightly charred and warmed through. Remove and cut into wedges (4–6 pieces per flatbread) for serving.

Finish and serve

Arrange the baked baguette croustades and grilled flatbread wedges around the warm four-cheese spinach & artichoke dip. Garnish the dip with remaining chopped parsley and an extra drizzle of olive oil if desired. Serve immediately.