Using a 1/4 cup measure, add batter to mason jars one scoop at a time. You only want to fill them up about half way, and the batter should work evenly for 4 jars. Again – don’t worry if it is perfect.
There is no set number of marshmallows to use, I pressed down as many as I could, about 4-5 each. Heat the broiler on your oven and watching carefully, brown marshmallows for about 1-2 minutes, or until golden brown.