Peel and puree ripe mango. Strain through a fine-mesh sieve, pressing firmly. Measure 240 ml (1 cup) strained puree. Set aside.
Heat cream, milk, and fine salt in a heavy saucepan until steaming. Do not boil.
Whisk egg yolks and sugar until pale and slightly thickened, about 90 seconds.
Temper: ladle ½ cup hot cream into yolks while whisking constantly. Repeat with a second ladle.
Return to saucepan. Cook over medium-low, stirring constantly, to 170–175°F (nappe).
Remove from heat. Let cool to 160°F. Stir in tequila, Triple Sec, and lime juice.
Whisk in mango puree and vanilla until fully incorporated.
Strain through a fine-mesh sieve. Press plastic wrap onto surface. Chill 4 hours or overnight.
Churn 20–25 minutes until soft peaks form.
Transfer to container. Sprinkle flaky sea salt over top. Press plastic wrap onto surface. Freeze 4 hours.