Against the Classical Sicilian with 6.Bc4 e6 
(1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6 6.Bc4 e6) 
Santos recommends the flexible 7.Be3 aiming for 0-0-0 if playable. 

A sample line from the free Short and Sweet version of the course, 
annotations by Santos, a bit shortened: 
7.Be3 Be7 (most common but not most accurate) 8.Qe2 0-0 
9.0-0-0 a6 10. Nxc6 (a fresh idea and even better than 10.Bb3) bxc6 
11.Bc5 N (preparing e4-e5) e5 12. Rd2 Qc7 13.Ba3 Rd8 
14.Rhd1 (the pressure on d6 paralyzes all Black pieces). 

I have been mostly interested in the Najdorf with 6.Be2, 
but 7.Be3 against the Classical Sicilian looks very interesting, too. 

To buy or not to buy 
the full version of Santos' course, 
that's the question.

One of the positions I see (by clicking on "Positions") takes me back -- it's from Tseshkovsky-Browne, Manila (izt) 1976, right before 14. Nxe6. "Suddenly Tseshkovsky's Knight ended up on K6 and Walter had to realize that the 'Russian analytical machine' had turned in a pretty good job." -- Kavalek

As for 6. Be2 e5 in the Najdorf, I see that he apparently goes with 7. Nb3 Be7 8. Be3 Be6 (8...0-0 9. g4, which I note was given as leading to an edge for White in the 2021 ECO reboot) 9. Nd5 Nbd7 10. Qd3.

(A reviewer [under "Reviews"] thinks this originates with Geller yet is "relatively new." Well, it seems Geller never played it, though he was certainly known for playing 6. Be2. And this kind of thing -- 10...0-0 11. 0-0 Bxd5 12. ed [a position Santos has had a couple of times in Titled Tuesday] -- is a book line going back decades.)