Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat.
Spread the pecan halves evenly on the prepared baking sheet. Toast them in the preheated oven for about 8-10 minutes, or until they become fragrant. Keep an eye on them to prevent burning.
In a medium saucepan, melt the butter over medium heat. Once melted, stir in the granulated sugar, vanilla extract, and salt. Cook, stirring constantly, until the mixture starts to boil.
Reduce the heat to low and continue cooking, stirring constantly, for about 3-4 minutes. The mixture should thicken slightly and turn a golden brown color.
Pour the hot butter and sugar mixture over the toasted pecans on the baking sheet, spreading it out evenly to coat all the pecans.
Immediately sprinkle the dark chocolate chips or chunks over the hot mixture. Let them sit for a couple of minutes to soften, then use a spatula or the back of a spoon to spread the chocolate evenly over the pecan mixture.
If desired, sprinkle a bit of flaky sea salt over the chocolate layer for a sweet-salty contrast.
Allow the bark to cool completely at room temperature until the chocolate sets. You can speed up the process by placing the baking sheet in the refrigerator for about 30 minutes.
