Preheat the oven to 350?F. Lightly grease a 9-inch round ovenproof chafing dish and set aside.
Bring a medium pot of water to a boil. Add the spinach in batches and cook until wilted, 2 to 3 minutes. Drain and refresh under cold running water. Squeeze the spinach to remove excess water and chop. Set aside.
Melt the butter in a medium pot over medium-high heat. Add the onions and cook, stirring, for 3 minutes. Add the garlic, salt, black pepper, and cayenne and cook, stirring, for 1 minute. Add the flour and cook, stirring constantly, to make a light roux, about 2 minutes. Add the milk and cream in a steady stream, and cook, stirring constantly, until thick and creamy, 2 to 3 minutes. Add the cooked spinach and lemon juice and stir to incorporate. Add the cubed Brie and grated Monterey Jack cheeses, artichoke hearts, and bacon and stir well. Remove from the heat and pour into the prepared dish. Top with the Parmesan cheese and bake until bubbly, about 10 minutes. Remove from the oven and serve hot with chips.
Makes 6 to 8 servings