How can I use one casting of vampiric touch more often?
As far as I understand it, vampiric touch does the following:
Casting the spell takes an action (leaving the caster a bonus action, a reaction and a move left to do in no particular order)
For the duration of said minute (10 rounds) one has a chance to apply 3d6 necrotic damage and heal 1/2 of that, up to ten times via "melee spell attack".
How could I acquire more "melee spell attacks" per round?
Rangers', Fighters', Paladins' and Bards' (College of Valor) Extra Attack doesn't qualify and neither do Monks' Flurry of Blows, because none are "melee spell attacks". Even the spell haste won't work and that is practically a minute-long use of Action Surge.