1 to 2 large sweet yellow onions (about 1 pound), peeled, cut into 3/8-inch slices (rings)
2 cups buttermilk
3 tablespoon Dijon mustard
2 eggs, beaten
¼ cup corn starch
2 cups Panko bread crumbs
1 teaspoon kosher salt
½ teaspoon freshly cracked pepper
In large bowl stir together onion rings, buttermilk, and Dijon mustard. Set in refrigerator at least 1 hour.
Meanwhile, place vegetable oil in fryer; cover and preset for onion rings at 375ºF.
Place corn starch in pie plate. Place beaten eggs in second pie plate.
In large bowl stir together all breading ingredients.
To coat onion rings: One at a time, remove an onion ring from buttermilk mixture. Coat with corn starch, then coat well with beaten egg. Next, coat with breading mixture; set breaded rings on cooling rack. Repeat with remaining onion rings.
Carefully place large frying basket into hot oil. Place about 6 onion rings in fryer. Cover; cook for preset time of 4 minutes or until batter is golden brown. Remove cooked onion rings from basket and let cool slightly on paper towel lined plate to absorb excess oil. Repeat with remaining coated onion rings. Refrigerate leftovers.