Season the filets to taste with Creole seasoning. Melt the butter in a skillet over medium-high heat and, before it can get a chance to brown, add the filets. (You might need to do this in two batches.) Cook to just below the desired degree of doneness.
Lower the heat to medium-low. Add the brandy to the pan and bring to a boil. (See precaution below.) After the alcohol has boiled off (about a minute), whisk the pan to dissolve the browned bits of beef and the butter.
Add the mushrooms, tomatoes, salt, pepper, marjoram and tarragon and simmer for about four minutes, until the mushrooms are tender. Add the green onions and parsley and cook about another minute. Turn off the heat.
Slice each filet across into two slices. Put the filet slices into the sauce and let them sit in the sauce for a few minutes.
Toast the bread. Place a filet slice on a slice of bread, and add a little sauce. Add another slice of filet and more sauce. Top with another slice of bread.