Mince the jalapeños and set them aside. Reserve some for garnish.
In a large, heavy saucepan, heat the butter over medium heat.
Add the jalapeños, onion, and garlic and sauté, stirring, until vegetables are softened (not browned).
Remove the pan from heat and stir in the avocado, tomatoes, and cream.
Lower the temperature and return the pan to heat, watching and stirring, so the cream does not separate.
Bring the soup slowly back to a simmer and cook, uncovered, for about 50 to 60 minutes or until reduced by one-third. Stir on occasion to prevent scorching.
Season, taste, and balance flavor.
Just before serving, stir in the chopped cilantro, reserving some for garnish.
Serve up in bowls and garnish with remaining cilantro and jalapenos.