Grease a 7x11 rectangle pan and set it aside (or your choice of pan). I also like to measure out the marshmallows at this point.
In a medium pot, over low-medium heat, add the butter and melt down. Add in the marshmallows and melt until smooth then add in the cake batter extract and salt. Mix well to incorporate.
Remove from heat and mix in the rice crispy cereal, reserved 1/4 cup marshmallows (not trying to melt the marshmallows but leave them whole) and sprinkles.
Mix altogether until evenly distributed then spoon into the prepared baking dish.
Using a buttered spoon or greased hands, press into the pan and add extra sprinkles on top if desired.
Allow to cool slightly then cut into it and serve!