Phenylpropene O-methyltransferase that catalyzes the methylation of the para-4-hydroxyl of chavicol to methylchavicol. Can also convert eugenol to methyleugenol but with less affinity. S-adenosyl-L-methionine + trans-isoeugenol = H(+) + S-adenosyl-L-homocysteine + trans-isomethyleugenol Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Specifically expressed in the peltate glandular trichomes on the surface of the young basil leaves. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family. COMT subfamily.