Rapid furnace experience

I was just smelting some food then I discovered this glitch.

To do this glitch get some raw food and the cooked food that your raw food will turn into when smelted. Put the food in a furnace to smelt it. Once the sum of the cooked food in the furnace and the cooked food in your inventory is more than 64, rapidly try to move the cooked food in the furnace to the slot of the cooked food in your inventory. Doing this too slow will stop this glitch