Hot Spinach-artichoke dip

1/2 cup butter or margarine
1 medium onion, chopped
2 - 10 oz. pkgs. frozen chopped spinach, thawed and well drained
1 14 oz can artichoke hearts, drained and chopped
1 8 oz. pkg cream cheese
1 cup sour cream
1 cup shredded Monterey Jack cheese
1 cup grated parmesan cheese
Tabasco Sauce to taste
salt and pepper

Melt butter in large skillet.  Add onion and cook until soft.  Stir in spinach, artichokes, cream cheese, sour cream, jack cheese and parmesan cheese.  Stir until smooth and creamy.  Add Tabasco, salt and pepper.  Pour into casserole dish top with more jack cheese and/or parmesan cheese and bake until cheese is melted and starts to brown.  Or put dip in small crock pot to keep warm.