Mint-Truffle Ice Cream Terrine with Mint and Chocolate Sauces

Bring cream to simmer in heavy large saucepan; remove from heat. Add chocolate; let stand 1 minute. Whisk until mixture is smooth. Whisk in extract. Freeze until firm, about 4 hours, or chill overnight. Line baking sheet with foil. Drop scant 1 tablespoon chocolate mixture for each of 16 truffles onto prepared sheet. Dust hands with cocoa; roll chocolate mounds into rounds. Cover and freeze truffles. Cover and chill remaining chocolate mixture for sauce. (Truffles and sauce can be made 2 days ahead.) Line 8 1/2x4 1/2x2 1/2-inch metal loaf pan with plastic wrap, leaving long overhang. Spread 1/3 of ice cream (about 1 2/3 cups) over bottom of prepared pan. Press 8 truffles in random pattern (and spaced apart) into ice cream layer. Spread 1/2 of remaining ice cream over. Press remaining 8 truffles in random pattern (and spaced apart) into second ice cream layer. Spread remaining ice cream over. Cover terrine with plastic wrap overhang. Freeze at least 6 hours and up to 2 days.