Cook scallion whites, vegetable oil, red pepper flakes, sesame seeds, and
pepper in a small saucepan over low heat, stirring occasionally, until oil is sizzling and scallions are golden brown, 12 - 15 minutes; let chili oil cool in saucepan.
Cook marijuana and
butter in a small saucepan over low heat until butter is melted; add 1 cup water and bring to a gentle simmer (the water keeps the mixture from getting too hot, which is key to preventing the herb from burning).