*10-15hcp, 4+♠, <4♥, could have longer minor
After recovering from the shock of your partner opening your 6 card suit, you have to decide what you do on this hand. Well, there are plenty of options and I'll give them to you.
1NT: GF relay
2NT: Raise to 3+ ♠, 4+ card support
4♥: Splinter
4♠: To Play
4NT: RKCB
5♥: Exclusion
There are other bids, but they are not so palatable. Even if you wanted to psyche 2♥, it's NF in our system.
Of course if you relay, you can find out partner's entire hand if uncontested.
If you bid 2NT you can get a picture of p's hand type (bal, 2 suited, or shortness), ask keycards, and then scan for specific K's and sometimes Q's.
I believe the other bids are self explanatory.
Your call?
1♠* - (P) - ?