Combine ground chicken, sage, shallot, spices, salt, pepper, egg, and panko in a large bowl.
Mix gently with your hands until just combined - do not overmix.
Form into 6 equal patties, about 3/4-inch thick.
Press a shallow dimple in the center of each patty with your thumb.
Heat avocado oil in a large skillet over medium-high heat until shimmering.
Add patties to pan, leaving space between them. Work in batches if needed.
Cook 5-6 minutes on first side without moving until golden brown.
Flip and cook another 5-6 minutes until internal temp reaches 165F.
Let patties rest briefly before serving on buns with mustard or over salad.