In a large stockpot of boiling water, add spinach and cook until bright green, approximately one minute. Drain and squeeze out excess water. Coarsely chop and set aside.
In a straight-sided sauté pan or sauce pot, melt butter over medium heat. Sauté onions until soft and tender, then add garlic and cook for another minute. Add flour and cook for another minute, until no flour is visible. Pour in cream, milk, wine and, stirring constantly, cook until thickened. Remove from heat and stir in Parmesan and Worcestershire sauce. Season with salt and pepper.
Meanwhile, mix together spinach, artichokes, and sour cream. Pour warm cream mixture over spinach, add white cheddar, and combine thoroughly. Season again, to taste.
Serve warm with tortilla chips, pitas, or crudité and sides of salsa and sour cream. To reheat, warm in a saucepan over medium low heat.