I am looking for some references where this variation is analysed. I have found some YouTube videos where engines play out this position, but they do not explain alternative moves which also lead to extremely complex games. It is called Kholmov System and arises from the Pirc Defence, but is also reachable from the Modern and Alekhine Defence (I almost always get it from the Alekhine).
[fen ""] 1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Bc4 Bg7 5. Qe2 Nc6 6. e5! Nxd4 (6...Nfd7 7. e6!? (7. Nf3)) (6...Ng4 7. Bb5) 7. exf6 Nxe2 8. fxg7 Rg8 9. Ngxe2
The engines claim Black is better, but in human practice White wins by a huge margin. Perhaps some book has good analysis of this variation?