Melt chocolate chips in a microwave-safe bowl, heating in 20-second intervals until smooth. Line a muffin tin with muffin liners, then spoon about 1.5 tablespoons of melted chocolate into each liner, spreading it up the sides evenly. Refrigerate for about 30 minutes until hardened.

Whisk together egg yolks and granulated sugar until pale. Heat heavy cream in a saucepan until just steaming, then temper egg mixture with hot cream. Return to heat until slightly thickened, then stir in melted chocolate and chill for 1-2 hours.

Whip additional heavy cream until stiff peaks form, then gently fold it into the cooled chocolate mixture.

Combine white sugar and corn syrup in a saucepan, stirring until sugar caramelizes to a deep amber color. Add butter and cream, stirring until smooth. Let cool slightly.

Remove chocolate cups from the refrigerator. Layer salted caramel and chocolate mousse, topping with more caramel and sprinkling with kosher salt.

Refrigerate assembled cups for at least 4 hours. Garnish with chocolate curls just before serving.