I would also bid 2C. I think that my auction would start 1H - 2C - 2D - 2H - 3H. Now opener has shown 6+ hearts and 4+ diamonds, responder has shown a gameforcing hand with 3+ hearts, and either clubs or a balanced hand. Then responder would bid 3NT (spade cue with serious slam interest). The complete auction might be: 1H - 2C 2D - 2H 3H - 3NT 4D - 4H (I know partner is missing a club control and I have one, but I am quite minimal for 3NT) 4S - 4NT 5D - 5S (queen ask, all keycards) 6D (♠A, ♥AQ, ♦AK) - 7NT (can count 14 tricks if hearts run)