I went to the store and I found these cute little jelly jars on sale for $3.99! That is a really good price, so I had to buy them. I was going to link you to a source online to purchase jars, but they are so much more expensive. You are better off keeping an eye on the prices in your grocery store.
1st- I mixed 1 egg into the second half of the mix and enough water to give me a slightly thicker than cake batter consistency. If you make these with a box of cake mix without making the failed cobbler first, just make the recipe on the box, substitute butter for the oil and put a little less water than it calls for to make a little thicker batter.
2nd- Put 2 T. of the batter into the jar. No more, or it will overflow in your microwave.