Is this an appropriate f6 break?

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ThrillerFan
Jeremy15KO wrote:
 

No - 7...cxd4 8.cxd4 Nb4!

However, as others have already mentioned, 6...cxd4 and only then 7...Bd7 is correct.

Also, you say about taking on f6 with the Knight.  If White is intelligent at all, he wouldn't take on f6!  He will maintain his strongpoint on e5.  In your proposed position, the only move I'd even remotely consider as White are 8.dxc5 and 8.O-O, never 8.exf6 in a million years!