The hosts broke the deadlock when Tammy Abraham rose to head in his 11th Premier League goal of the season (24) against the side he scored 26 times for on loan in the Championship last season.
But Dean Smith's side levelled against the run of play before half-time as Trezeguet scrambled the ball over the line from close range (41).
Chelsea were back in front three minutes after the restart when Mount struck in style and the Blues held on for their first victory in four games.
The result puts Chelsea six points clear of fifth-placed Wolves but, perhaps more significantly, eight clear of Manchester United and nine ahead of Tottenham. Aston Villa remain 15th after their two-match unbeaten run was ended in west London - a point above the relegation zone after Southampton's win over Norwich.
Chelsea: Kepa (7), Azpilicueta (7), James (7), Christensen (6), Zouma (7), Kante (7), Mount (8), Kovacic (6), Willian (8), Pulisic (7), Abraham (8).
Subs: Jorginho (n/a), Hudson-Odoi (n/a), Batshuayi (n/a).
Aston Villa: Heaton (7), Targett (6), Elmohamady (7), Mings (7), Konsa (6), Nakamba (6), McGinn (6), Grealish (6), Hourihane (5), Trezeguet (7), Wesley (5).
Subs: Luiz (6), Jota (6).
Man of the match: Mason Mount.
- Chelsea have lost just one of their last 56 Premier League home games against newly promoted teams (W45 D10 L1).
- Aston Villa have picked up just one point from their last 42 available in away games against sides starting the day in the top four (W0 D1 L13).
- Tammy Abraham has scored 11 goals in 14 Premier League appearances this season - the only Chelsea players to score more in their first 14 apps in a single PL season are Diego Costa (12 in 2014-15) and Nicolas Anelka (12 in 2008-09).
- Only Jamie Vardy (17) has been directly involved in more Premier League goals this season than Chelsea's Tammy Abraham (14 - 11 goals, 3 assists).
Chelsea travel to face Everton at Goodison Park in the Premier League on Saturday; Kick-off is at 12.30pm.
Meanwhile, Aston Villa host Leicester on Renault Super Sunday; coverage starts on Sky Sports Premier League and Main Event at 1pm with kick-off at 2pm.