Meanwhile, in deep 10-inch skillet, heat 3 tablespoons olive oil over medium heat until hot. Add sliced leek, garlic, marjoram and thyme. Cook about 3 minutes, stirring occasionally, until onion is softened. Add cream and cream cheese. Simmer about 3 minutes or until thickened. Remove from heat. Stir in Mexican sour cream, and season with salt and pepper. Pour over squash in baking dish.