Preheat oven to 350°. Grease an 8" square baking dish with 1 tbsp. of the butter and set aside. Put sugar, cinnamon, scallions, cilantro, and 4 cups water into a heavy medium saucepan and stir well. Boil over high heat until syrupy and reduced by about two-thirds, 25-35 minutes, watching pot carefully to make sure syrup doesn't become too thick. Strain syrup, discarding solids, and set aside.
Butter toast with 1 tbsp. of the butter. Put half the toast, buttered side up, in bottom of prepared dish in a single layer. Sprinkle half the raisins, then half the cheese, over toast. Cut remaining butter into small pieces. Scatter half the butter over cheese and raisins in dish, then pour half the syrup evenly on top. Repeat layering process with remaining toast, raisins, cheese, butter and syrup.
Bake until pudding is bubbling hot and cheeseis lightly browned on top, 20-25 minutes. Serve warm with a dollop of sour cream or a scoop of vanilla ice cream, if you like.