Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius). Spread the pecan halves in a single layer on a baking sheet and place them in the preheated oven. Toast for 8 to 10 minutes, checking and stirring once halfway through, until the pecans are fragrant and just beginning to darken very slightly. Watch them carefully during the last few minutes — pecans can go from perfectly toasted to burned quickly, and they will continue cooking briefly from residual heat after you remove them from the oven. Toasting the pecans is genuinely the single most important step in this recipe: it deepens their natural buttery flavor dramatically, removes any lingering bitterness, and produces a toasted nuttiness that pairs with the caramel and chocolate in a way that raw pecans simply cannot match. Allow the toasted pecans to cool completely before proceeding.
Step 2: Arrange the Pecan Clusters
Line a large baking sheet with parchment paper. Arrange the cooled toasted pecans into small clusters of 4 to 5 nuts each, spacing the clusters about 2 inches apart to give the caramel room to spread slightly without the clusters merging. Each cluster should be arranged so the nuts are touching and overlapping slightly — they should form a compact, roughly round nest rather than a loose arrangement. You should get approximately 20 to 24 clusters from this recipe, depending on how generously you portion them. Set the prepared baking sheet aside in an accessible location so you can work quickly once the caramel is ready.
Step 3: Make the Caramel
Combine the sweetened condensed milk, butter, and salt in a medium heavy-bottomed saucepan over medium-low heat. Cook, stirring constantly with a heatproof spatula or wooden spoon to prevent the mixture from scorching on the bottom of the pan, for 8 to 12 minutes. As it cooks, the mixture will gradually thicken and deepen in color from pale cream to a rich golden amber. The caramel is ready when it has thickened noticeably and coats the back of a spoon, leaving a clean line when you draw your finger across it. If you want to use the cold water test — which is the most reliable indicator of doneness for this method — drop a small spoonful of the hot caramel into a bowl of ice water. If you can immediately lift it out and roll it into a ball between your fingers, the caramel has reached the soft ball stage and is ready. Remove from heat and stir in the vanilla extract.
Step 4: Apply the Caramel
Working quickly, because caramel thickens rapidly as it cools, spoon approximately 1 to 1 and a half teaspoons of warm caramel directly over each pecan cluster. The caramel should be fluid enough to flow slightly and touch each nut in the cluster, binding them together, while being thick enough to hold its shape and not spread dramatically beyond the edges of the cluster. Use the back of the spoon to gently coax the caramel into a roughly circular shape if needed. If the caramel begins to stiffen in the pan before you have finished all the clusters, return it to very low heat and stir gently to loosen it, or add a tiny splash of heavy cream and stir to incorporate. Allow the caramel-topped pecan clusters to rest at room temperature for 30 to 45 minutes, or until the caramel is firm and no longer sticky to the touch, before adding the chocolate layer.
