One note with two noteheads and two beams

see https://musescore.org/en/handbook/voices-0. (and you seem to mean stems, not beams), you'd also need sort of the opposite of https://musescore.org/en/handbook/shared-noteheads, probably achieved by simply selecting one of the note heads and using Shift+X on it, or by nudging it sideways (double click, Ctrl+right/left, the stem will follow after Esc, or using horizontal offset on the chord in Inspector.