step 01Line rimmed baking pan with parchment paper. Prepare cake as label directs in 13 x 9-inch pan; cool. In batches, break up cake into smaller pieces and pulse in food processor to small crumbs; transfer to mixing bowl.
step 02With hands, gradually work in evaporated milk, sweetened condensed milk, sour cream, whole milk and rum until mixture sticks together and does not crumble when rolled into a ball (mixture should resemble cookie dough). Roll cake mixture into 1-inch balls; place on prepared pan. Freeze 30 minutes or refrigerate at least 2 hours or up to overnight. Makes about 40 cake truffles.
step 03Melt white candy melts as label directs; stir in vegetable oil. Using a fork, dip cake truffles into white chocolate to completely cover; allow excess chocolate to drip off. Place on same pan; immediately sprinkle with cinnamon. Reheat melted chocolate as necessary if it begins to harden.
