To make peppermint oil, crush the fresh peppermint leaves with your hands or chop them using a knife. Thereafter, put it in a glass jar.
Pour olive oil over it and mix thoroughly.
Close the lid, shake the jar, and let it steep for about 1-2 weeks. Make sure to shake the jar at least once every day.
Strain the oil using a fine strainer or a cheesecloth in an airtight container.
Use the oil immediately or store it in a cool and dry place for 3-5 months.
Notes
You may keep repeating the entire process until the desired quantity of oil is obtained or you can take a large quantity in the first go itself. Remember, the ratio of peppermint leaves to oil should not be more than 1:1.