Line a large rimmed baking sheet with parchment paper or a silicone baking mat. This ensures the bark does not stick and makes cleanup very easy.
In a microwave-safe bowl, combine the semi-sweet and milk chocolate chips. Microwave in 30-second intervals, stirring in between, until the chocolate is completely smooth and melted.
Pour the melted chocolate onto the prepared baking sheet. Use an offset spatula or the back of a spoon to spread it into an even layer, about 1/4 inch thick.
In another microwave-safe bowl, combine the caramel bits and heavy cream. Microwave for 30 seconds at a time, stirring until the mixture is smooth and pourable.
Drizzle the melted caramel over the chocolate layer in a decorative pattern. Use a knife to lightly swirl the caramel into the chocolate if desired. Immediately press the toasted pecan halves into the mixture while it is still wet.
Sprinkle the flaky sea salt evenly over the top of the bark. Place the baking sheet in the refrigerator for at least 1 hour, or until the chocolate and caramel are completely firm.
Once set, lift the bark off the parchment paper. Use your hands to break it into rustic shards or use a sharp knife to cut it into even squares.