White’s knight is on a light square; Black’s king and knight also are on light squares and can be forked at e7. If you notice the forking idea at all here—in other words, if you aren't lulled into overlooking it because the target on c6 is another knight—you are most of the way home. Of course the knight is an unsuitable target, so you force Black to replace it by first taking it with another piece. Thus 1. QxN; QxQ; 2. NxB+. After playing out the fork White has won two pieces.