For the Chile Basil Ginger Sauce:
In a bowl, combine all of the ingredients and stir. Taste for seasoning and adjust with honey for sweetness or fish sauce for salt as desired. Cover and refrigerate until ready to serve. Can be refrigerated for up to 3 days.
For the Grilled Branzino:
Preheat Traeger grill to 450F for 5 minutes. Make sure the grill grates are very clean.
Rinse the fish under cold water and pat very dry with paper towel.
Using a sharp knife, make three diagonal score marks around 1” apart on both sides of each fish. Season the cavities with a pinch of salt and pepper, stuff each fish with 3 lime slices and half of the reserved cilantro stems. Tie each fish with three strands of butcher’s twine. Rub with avocado oil and generously season with salt and pepper.
Once your Traeger grill is preheated, place the fish as close to the front edge of the grill as possible, close the door and cook until lightly charred, around 6 minutes. Carefully flip with a fish spatula and pair of tongs and cook until lightly charred, around 6 more minutes. The fish is ready to serve when the flesh is opaque and flaky.
Transfer the fish to a serving platter and spoon the Chile Basil Ginger Sauce over top. Garnish with thinly sliced scallions and serve immediately.