Slice each chicken breast in half horizontally to yield 4 pieces of uniform thickness. This helps the chicken cook evenly.
In a small bowl, whisk together the orange juice, soy sauce, hoisin sauce, ginger, garlic, palm sugar, and salt until the sugar dissolves.
Place the chicken breasts in a glass or ceramic baking dish. Pour about 2 tablespoons of the marinade over the chicken, turning to coat all sides. Cover tightly with plastic wrap and refrigerate for at least 1 hour or up to overnight.
Transfer the remaining marinade to a small airtight container and refrigerate until ready to bake.
When you're ready to cook, preheat the oven to 375°F.
Discard the used marinade from the chicken. Arrange the chicken pieces in a clean baking dish and pour the reserved marinade over them.
Bake for 30–35 minutes, turning the chicken once or twice during cooking, until the internal temperature reaches 165°F and the sauce slightly thickens.
Remove from the oven and let the chicken rest for 5 minutes before serving.
Sprinkle with toasted sesame seeds and chopped chives, if desired, and serve warm.