Begin by slicing the seedless cucumber into thin rounds and placing them in a mixing bowl. In a small pot, combine rice vinegar, salt, and sugar, and heat over medium heat until the sugar dissolves, about 2-3 minutes. Remove from heat and add ice to cool the brine quickly. Pour this pickling mixture over the cucumber slices and refrigerate for at least 4 hours, or overnight for maximum flavor.

In a medium saucepan, heat sesame oil over medium heat. Sauté grated garlic and ginger for 1-2 minutes until fragrant. Then add low sodium soy sauce, gochujang, brown sugar, honey, and a splash of rice vinegar. In a small bowl, mix cornstarch with water to create a slurry, then stir it into the sauce. Bring to a simmer, cooking until thickened, about 5-7 minutes.

In a bowl, combine mayo with sriracha, sesame oil, and a dash of soy sauce. Mix well until all ingredients are fully incorporated and the sriracha mayo is smooth and creamy.

Preheat your grill to a medium-high temperature. Season the chicken thighs generously with BBQ rub. Grill for 5-7 minutes per side, flipping frequently to avoid burning. Move the thighs to indirect heat until the internal temperature reaches 165°F.

Spread a layer of sriracha mayo on both halves of your toasted sandwich buns. Place a sauced chicken thigh on the bottom half, then top with pickled cucumbers. Close the sandwich and serve immediately.