On medium-high heat saute the onions in the oil until translucent, then let them cool before you add them to the turkey
Combine the raw ground turkey with chopped onions, mustard, and all the seasoning. I use my hands to mix everything together
Shape into four patties and I poke a hole about half way through in the middle to prevent shrinkage
Cook on medium high heat on the grill, large skillet, or griddle and cook through, flipping 1/2 way through cooking time. About 5 minutes per side or until internal temperature is 165 degrees. You want a turkey burger to be cooked completely through