Microwave semisweet chocolate pieces and whipping cream in a 2-quart microwave-safe bowl at MEDIUM (50% power) 3 1/2 minutes. Whisk until chocolate melts and mixture is smooth. (If chocolate doesn't melt completely, microwave and whisk at 15-second intervals until melted.) Whisk in butter and liqueur; let stand 20 minutes.
Beat at medium speed with an electric mixer 4 minutes or until mixture forms soft peaks. (Do not overbeat mixture.) Cover and chill at least 4 hours.
Shape mixture into 1-inch balls; roll in Praline Pecans. Cover and chill up to 1 week, or freeze up to 1 month.
White Chocolate-Praline Truffles: Substitute 3 (4-ounce) white chocolate bars for semisweet chocolate bars and Praline Almonds for Praline Pecans.
Chocolate Marble Truffles: Prepare 1 recipe each of mixture for Chocolate-Praline Truffles and White Chocolate-Praline Truffles. Spoon both mixtures into a 13- x 9-inch pan; swirl with a knife. Chill and shape as directed; roll in cream-filled chocolate sandwich cookie crumbs, omitting Praline Pecans and Praline Almonds.
Note: We used Ghirardelli semisweet chocolate bars and Ghirardelli white chocolate bars; 2 cups (12 ounces) Hershey's semisweet chocolate morsels may be substitutes for semisweet chocolate bars.