Set oven to 350°F (175°C). Scatter pecan halves over a big baking tray and roast them for 10 minutes. Take them off the tray and cover the tray with parchment paper.
Place the roasted pecans on the parchment-covered tray in 34 distinct clusters, each measuring roughly 2 to 2 1/2 inches across.
In a 5-quart stockpot, put together light brown sugar, corn syrup, and butter. Heat over medium flame until boiling. Mix in salt, vanilla, and sweetened condensed milk. Keep cooking and stirring until a candy thermometer shows 240°F (115°C). Take off heat and allow to sit for 10 minutes so it thickens.
Drop about 3/4 tablespoon of caramel onto each pecan bunch. Put the tray into the fridge for 15 minutes so the caramel sets.
In a bowl safe for microwaving, mix milk chocolate chips with vegetable shortening. Microwave in 30-second bursts, stirring each time, until fully melted and silky. Take the caramel-covered pecans out of the fridge and drizzle roughly 1 tablespoon of chocolate over every cluster.
Place the sweets back into the fridge until the chocolate hardens. Serve once set.