Lightly beat the egg in a small bowl with a fork until the yolk breaks.
In a large bowl combine the ground turkey, beaten egg, panko breadcrumbs, onion powder, paprika, parsley, salt, and pepper.
Oil your hands lightly to prevent sticking and gently mix the ingredients by hand until just combined; avoid overmixing.
Divide the mixture into eight equal portions, shape into small round balls, then flatten each into a thin patty sized for sliders.
Cook the patties over medium heat on a preheated grill or in a skillet for about 3 minutes per side, until an instant-read thermometer registers 160°F (71°C) in the center.
If desired, top each hot patty with a slice of cheese to melt, then place on slider buns and serve.