When you use the stove and the menu comes up, you will notice a + and - sign to the left and right to each of the four burners. The negative sign closes one burner per click and the plus sign open one per click.

There is a quest where one of the marketplace vendors will want a delicious broth as teaching you how to cook and the mechanics of the stove help you to do this.

I have experimented with the stoves for several hours of game play to see how much cooking affect each recipe depending how many burners are opened or not and depending on the pot used, you want to either have all the burners fully opened, fully closed or in-between.

To get the delicious broth, you want to close all the burners in the slot you are cooking with. so far this seems to be the only recipe that quality can be changed using the burners. All the other recipes I have seen and experimented with so far do not seem affected in quality, only time for the burners such as the mash's. Closing all the burners for making mash takes six in game hours to cook but doesn't seem to change the quality of the mash. The Same goes for the meats with time being slow cooked or speed cooked but not changing the quality of the foods or drinks.
I do find it best when making broth, tea and coffee to close all the burners and when making anything in bigger pots opening all of the burners but not forgetting the food on the stove so it burns.