In a large skillet, toast the pecans over medium high heart for a few minutes.
Line 2 large baking sheets with parchment paper and spray with nonstick cooking spray.
Arrange the toasted pecans in groups of 3 leaving about an inch of space between each group. Set aside.
In a medium saucepan, melt the butter over medium-high heat.
Stir in the brown sugar, corn syrup, and sweetened condensed milk. Cook and stir continuously until it reaches 235-240F on a candy thermometer.
Remove from heat and stir in the vanilla.
Drizzle about 1/2 tablespoon of caramel over each cluster, set aside.
Fill a pot about 1/4 of the way with water, and fit with a bowl that wont touch the bottom of the pot to create a double boiler.
Heat the pot over medium heat.
After letting it heat up for a few minutes, start to stir the chocolate chips until they are fully melted and smooth.
Stir in the shortening and spoon about 1/2 tablespoon on the top of each cluster.
Once the chocolate has cooled serve immediately or store in an airtight container with parchment paper between each layer of clusters.