Bring cream and milk to a simmer in a medium saucepan. Add mint and steep for 1 hour. Strain and return to pan.

Preheat oven to 325 degrees. Whisk yolks and next 3 ingredients in a medium bowl. Bring mint cream to a boil; add dark chocolate. Remove from heat and whisk until melted. Return to a boil. Gradually whisk into yolk mixture. Strain into medium pitcher. Add salt.

Place 6 ramekins in a large baking dish or roasting pan. Divide mint custard among ramekins.

Pour hot water into dish halfway up sides of ramekins. Cover baking dish with a sheet of parchment paper. Bake custards until just set in center, about 40 minutes. Let cool in water bath. Cover; chill at least 2 hours or overnight.

For white chocolate ganache, stir white chocolate in a medium metal bowl set over a saucepan of simmering water until melted and smooth. Whisk in cream, vanilla and salt. Cover; chill until cold, about 2 hours.

When ready to serve, pour ganache over chilling pots. Garnish with a mini candy cane. Serve immediately.