Artichoke Spinach Dip

2 T. butter 1 (10 oz) pkg frozen, chopped spinach, partially thawed 1 (14 oz) can artichoke hearts, drained and chopped 1 (8 oz) pkg cream cheese, softened 1 (16 oz) pkg sour cream 1 c. grated Parmesan cheese garlic salt to taste Melt butter in a large saucepan over medium heat. Stir in the spinach and artichoke hearts. Cook until tender, about 5 minutes. Mix cream cheese and sour cream into the spinach mixture. Stir in Parmesan cheese and garlic salt. Cook, stirring occasionally until thickened (10-15 minutes). Serve warm.