Preheat oven to 350℉. Whisk together all ingredients except for chicken. Set aside. Rinse chicken and pat dry with a paper towel. Place chicken in a large casserole dish or roaster. Spread 3/4 of mustard mixture evenly over entire chicken.
Roast uncovered in preheated oven for 60 minutes. Brush chicken with remaining mustard coating and continue to roast for an additional 45-60 minutes or until an instant read thermometer registers 170℉ at the thickest part of the thigh. Remove from oven and cover with foil and allow to rest for 15-20 minutes. Cut chicken into pieces and serve immediately.
If using as a one pan meal, add evenly cut potatoes and other vegetables along with fresh herbs to the roasting pan after the chicken has cooked for 30 minutes. Turn vegetables when you brush the chicken with remaining mustard rub.
Roasting time will vary depending on the size of your chicken.
In a medium bowl, mix together egg, spinach, seasoning salt, onion powder and pepper Add mashed potatoes and mix until well combined. Stir in cheese, bread crumbs and chives. Mix until combined and bread crumbs have been absorbed.
Heat oil in a non stick frying pan over medium high heat. While pan is heating, form 1/3 cup potato mixture into approximate 3" patties about 1/2" thick and place into pan as you form them. Cook 4-5 minutes per side until heated through and golden brown.
Stir together sour cream and dill and season to taste with salt and pepper. Keep chilled until ready to serve with cakes.