Both horses are owned by financier Rich Ricci and trained by Irish champion trainer Willie Mullins.
Two-time Gold Cup runner-up Djakadam (4-5 fav) had to battle before taking the John Durkan Memorial Chase under jockey Ruby Walsh.
Douvan (1-6 fav) landed the Hilly Way Chase for jockey Paul Townend.
The six-year-old, who won last year's Arkle Trophy, is odds-on favourite for the Queen Mother Champion Chase next March and recorded a seventh win out of seven over fences.
BBC horse racing correspondent Cornelius Lysaght
After a quieter start than some seasons, which has allowed Gordon Elliott an early lead in the Irish trainers' title race, Mullins was back in characteristic full-flow mode on an important afternoon for he himself, his biggest owners and main jockeys.
Two horses from Michael O'Leary's Gigginstown House operation - with which Mullins has split - threw everything at Djakadam, but he repelled them in a manner that bodes well for the attempt to make it third time lucky, after two seconds, in the Cheltenham Gold Cup.
Douvan was untidy at one fence, but still breezed home at Cork and clearly deserves his odds-on status for Cheltenham's Queen Mother Champion Chase.
Stablemates Djakadam and Douvan, two of the biggest hopes for the Cheltenham Festival, won Sunday's feature races at Punchestown and Cork respectively.