Preheat your oven to 350°F (175°C). Spread the pecan halves on a baking sheet and toast for 8 to 10 minutes, or until fragrant and slightly darkened. Remove from the oven and let them cool completely.
Line a clean baking sheet with parchment paper. Arrange the toasted pecans into 18 small clusters of 3 to 4 nuts each on the paper.
In a heavy-bottomed saucepan over medium heat, melt the sugar, stirring constantly with a spatula. Once the sugar has fully liquefied and turned a deep amber color, immediately remove from the heat.
Carefully stir in the butter and heavy cream. The mixture will bubble vigorously, so be cautious. Return the pan to low heat and stir until the caramel is smooth and reaches 240°F (115°C) on a candy thermometer.
Remove the saucepan from the heat and stir in the vanilla extract and fine sea salt. Allow the caramel to cool for 5 minutes so it thickens slightly.
Spoon a generous amount of caramel over each pecan cluster on the parchment paper.
Melt the chocolate chips in a microwave-safe bowl in 30-second intervals, stirring between each, until completely smooth.
Drizzle the melted chocolate over the set caramel clusters and sprinkle immediately with a pinch of flaky sea salt before the chocolate hardens.
Let the clusters sit at room temperature for at least 1 hour until the chocolate and caramel are firm.