Use your knife and cut your soap base into small chunks.
Put the chunks into a microwave-safe container.
Microwave in 30-second increments until completely melted.
Add a few drops of peppermint essential oil. Stop adding based on your preference for the strength of the scent.
Pour the melted soap into the mold.
Add a few drops of colorant to the melted soap.
Swirl the colorant and melted soap with a toothpick until you reach the desired color.
Allow your soap to cool completely, then remove it from the mold.