In online games I sometimes have this happen:
[fen ""]
1.d4 d5 2.c4 c6 3.Nf3 e6 4.Nc3 dxc4
and Black plays the famous "Noteboom variation". I checked my database and I have in fact lost every single game as White where this variation happened. Usually Black just arranges his pieces nicely and pushes the a-pawn and b-pawn and I lose material due to pieces getting trapped in the corner, or having to give up pieces to stop the pawns promoting.
What is a promising way to meet this system for White?
Note: Of course, I could avoid the line with 4.e3 going into a normal Meran. But I often play quickly the first few moves of an internet game and carelessly make a natural developing move with the knight. It would be good to know how to recover from this.
4. Nc3
is perhaps the main move, and you shouldn't give it a dubious mark.