1 cup butter
1 cup light corn syrup
2 1/3 cup packed brown sugar
14 oz can sweetened condensed milk
1 tsp vanilla
1 1/2 pounds pecans
3/4 cup milk chocolate chips
3/4 cup semisweet chocolate chips
4 tbsp shortening
Line baking sheets with wax paper; lightly coat with nonstick cooking spray and set aside. Cube the butter and place in a saucepan. Add the syrup, brown sugar, and salt. Cook and stir until sugar is melted.
Gradually stir in the milk. Cook and stir over medium heat until mixture comes to a boil; a candy thermometer needs to read 248 degrees (hard ball stage). Remove from the heat; stir in the vanilla. Gently stir in the pecans. Drop by rounded teaspoonfuls onto prepared baking sheets. Refridgerate until firm, about 12 minutes.
In a microwave-safe bowl, melt the chocolate chips and shortening. Stir until smooth. Drizzle over the clusters. Chill until firm. Store in the fridge.