Popping popcorn with butter rather than oil is a tricky process. The burning point of butter is much lower than that of oil, which makes it difficult to work with. Popcorn kernels usually pop when the internal temperatures inside the kernels reach about 232 degrees Celsius. The liquid temperature must stay around 65.5 to 93.3 degrees C to produce enough pressure to pop the corn. Most popcorn experts recommend using oil to pop the kernels because oil has a higher burning temperature. However, it is possible to pop popcorn with butter as a base if you proceed carefully.
Melt three to five tablespoons of butter in a small pot over low heat. You do not want to heat the butter enough to cause it to turn brown or bubble.
Pour the butter into the larger pot. Place two or three kernels of corn into the butter. This next part is very tricky. You have to heat the butter to around 65.6 degrees Celsius before the popcorn can pop. However, the butter can easily burn at such a high temperature.
Stir the butter constantly while keeping the stove at medium low to medium heat. Place a kitchen thermometer inside the butter to gauge the temperature. When the temperature reaches around 65.6 degrees C, the kernels should start to pop.
Cover the bottom of the pan with kernels after the test kernels pop. Remove the test kernels before putting in the new kernels to prevent them from burning. Place the lid on the pot.
Shift the pot around on the stove constantly to prevent the butter from burning as the kernels pop. Continue to move the pot around as the kernels pop. You may have to hold down the top of the lid to prevent the kernels from popping out of the pot or lifting the lid right off the pot. Use a hot pad as necessary to prevent burning your hands. When the kernels stop popping for one to two seconds, the popcorn is done. Remove it immediately or else it will start to burn.
This process is very delicate and it may take several attempts before you stop burning the butter. Butter can burn easily, which is why it is not usually recommended as a base for popcorn popping.