Turn Instant Pot on Saute mode and add butter, ketchup, Worcestershire sauce, sugar, salt, chili powder, paprika and dry mustard. Whisk until butter has melted.
Add chicken to Instant Pot and cover with lid. Select Poultry mode.
When cooking time is done, let the Instant Pot do a natural release of pressure.
Remove chicken and shred with fork. Add chicken back into pot with the sauce and stir to cover chicken with sauce.
Serve with rice, on a bun, a taco shell or mashed potatoes.