How many menus include puree of split peas aux croutons?
puree of split peas aux croutons is a name of dish;
SELECT SUM(CASE WHEN T1.name = 'Puree of split peas aux croutons' THEN 1 ELSE 0 END) FROM Dish AS T1 INNER JOIN MenuItem AS T2 ON T1.id = T2.dish_id