The winger came off the bench for his first-team debut at Forest Green in the Carabao Cup earlier this month.
Now John Mousinho has named the second-year scholar in his starting XI against Fulham Under-21s in the EFL Trophy.
Mottoh is among 11 changes to the side held by Cheltenham to a goalless draw on Saturday.
Those handed recalls include Christian Saydee, Abu Kamara, Jack Sparkes and Paddy Lane, who all came off the bench in that Fratton Park stalemate.
Others featuring are Ryan Schofield, Sean Raggett, Zak Swanson, Ryley Towler, Ben Stevenson and Terry Devlin.
Pompey’s substitutes consist of youngsters Brian Quarm, Bastian Smith and Mitch Aston.
There is also a place for Sam Folarin, who has been recalled from a Poole Town loan spell which saw him struggle to get match minutes.
Pompey: Schofield, Swanson, Raggett, Towler, Sparkes, Stevenson, Devlin, Kamara, Mottoh, Lane, Saydee.
Subs: Smith, Quarm, Poole, Aston, Robertson, Scully, Folarin.