Make the honey mustard sauce first. Combine mustard, honey, ¼ cup brown sugar, and apple cider vinegar in a small saucepan. Simmer for 10 minutes. Season with ½ tsp. salt, ½ tsp. garlic powder, and ¼ tsp. black pepper. Set aside to let cool.
Make the rub for the chicken. In a small bowl, combine cumin, brown sugar, paprika, mustard powder, salt, and pepper. Use a fork to mix well. Sprinkle the chicken breasts with the rub and coat evenly. Let sit for 5 minutes.
Turn your multi-cooker* to the sauté mode. Add the olive oil and allow to heat up, then add the chicken breasts (in batches if necessary). Brown on both sides. Remove from multi-cooker and repeat with remaining chicken breasts, if necessary.
*To prepare in a slow-cooker:
Place seasoned chicken breasts in slow cooker and top with chicken broth. Cover and cook on low for 6-7 hours or high for 3 hours, until chicken is cooked through and tender. (Skip to step 6.)
Add 1/2 cup chicken stock (or water) into the multi-cooker, then add back the seared chicken breasts and 1/2 cup of the prepared honey mustard sauce.
Secure lid on multi-cooker. Make sure the vent is in the seal mode. Select “high pressure” on the multi-cooker and set for 10 minutes. Let cook for 10 minutes, then turn off multi-cooker and allow the pressure to release naturally for 10 minutes.
Carefully transfer cooked chicken breasts from multi cooker onto a cutting board and shred using two forks. Return shredded chicken to multi-cooker and recombine with the cooking liquid.
Serve multi-cooker shredded chicken on Martin’s Big Marty’s Rolls topped with reserved prepared honey mustard sauce.