Cut chicken fillets into 1/2-inch thick slices; cook in 1 tablespoon olive oil on medium-high heat until it loses its pink color and begins to brown, about 10 minutes. Add barbecue sauce, reduce heat to medium, and continue cooking uncovered until chicken has soaked up most of the sauce.
In the meantime, prepare onion and mushrooms. In a medium skillet, add remaining 1 tablespoon oil; turn heat to low. When oil is hot but not smoking, add onion, and cook until caramelized, approximately 15 minutes. Add mushrooms, and continue cooking until mushrooms release moisture and are tender, approximately 6 more minutes.
Place slightly warmed buns or rolls on a prep space; evenly distribute chicken slices. Next, top chicken with onion and mushrooms. Top off sliders with Creamy Cabbage and Bok Choy Cole Slaw. Add salt to taste.
