Preheat the oven to 375°F. Line a baking sheet with parchment paper.
To make the garlic toast: Split the loaf in half horizontally and place the two halves cut side up on the prepared baking sheet.
Stir together the melted butter and garlic and drizzle over the bread.
Bake until it begins to brown, about 20 minutes. Sprinkle the Parmesan on top and bake until melted and bubbling, about 5 minutes. Remove from the oven and sprinkle the parsley on top. Cut into triangles or wedges.
Meanwhile, prepare the baked spinach artichoke dip: If using thawed frozen spinach, wrap it in a clean kitchen towel and squeeze it tight to extract as much liquid as possible. Set aside.
If using fresh spinach, place it in a large sauté pan with a lid and add 2 tablespoons water. Set the pan over medium-low heat and cook until wilted, using tongs to turn the spinach over as it wilts, moving the uncooked leaves on top to the bottom of the pan to cook them. Cover the pan and steam for 2 minutes. Remove the pan from the heat and drain the spinach in a colander. Let stand until cool enough to handle, then wrap the spinach in a clean kitchen towel and squeeze it tight to extract as much liquid as possible. Finely chop the spinach.
Place the artichokes in a large bowl and smash them well with a fork, removing any tough leaves. Add the spinach, pulling it apart with your fingers or the fork. Add the cream cheese, mayonnaise, Parmesan, Gouda, garlic, and white pepper and stir well until combined.
Transfer the mixture to a pie plate and smooth the top. Sprinkle the dill and paprika on top.
Bake until bubbling and hot, about 20 minutes. Turn the broiler to high and broil until the top is nicely browned. This will happen quickly, so watch carefully and do not step away.