4 tablespoons unsalted butter, plus more for the pan
2 (10-ounce) packages fresh spinach, well rinsed and stems trimmed
1 cup chopped yellow onions or leeks
1 tablespoon minced garlic
2 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1/4 teaspoon cayenne
1/4 cup all-purpose flour
1 cup milk
1 cup heavy cream
2 teaspoons freshly squeezed lemon juice
1 cup 1/2-inch cubes of Brie
1 cup grated Monterey Jack
1 (6 1/2-ounce) jar marinated artichoke hearts, drained and chopped
4 strips bacon, cooked until crisp, drained, and chopped
1/4 cup grated Parmesan
Assorted chips (pita chips, tortilla chips, bagel chips) or sliced baguette, for dipping