The rarest of the knight retreats in this position of the Petroff Defense. White's idea is to exchange queens and press an endgame that is close to equality. Honestly, it's a choice closer to Carlsen's style than Vachier-Lagrave's, but the French GM will show that he can play technical endgames with the same skill he plays dynamic middlegames.
1. e2e4  1... e7e5  2. g1f3  2... g8f6  3. f3e5  3... d7d6 