Melt the butter in a large saucepan. Saute the onions, seasoning with salt and pepper. Cook about five minutes. Pour in the stock and bring to a boil, lower heat and simmer 10 to 12 minutes add the blossoms and cook 5 minutes longer.
Transfer soup to food processor and puree until smooth. Strain soup back into saucepan. Pour in the half and half and bring to a boil. Season with salt and pepper.
Serve hot, garnished with the cheese and lime wedges.
Have a hankering for a Traditional Bocadillo? Try Zingerman's in New York City. Some typically Spanish ingredients include: