01 - In a medium bowl, whisk together honey, whole grain Dijon mustard, and 1/4 cup water until fully blended.
02 - Place chicken thighs in a large slow cooker and pour honey mustard mixture over the chicken. Toss to coat evenly.
03 - Cover and cook on low for 4 to 4.5 hours, or until chicken is fully cooked and tender.
04 - In a small bowl, dissolve cornstarch in 2 tablespoons water. Add slurry to slow cooker. Shred chicken using two forks, stir well, and cook for an additional 20 minutes until sauce thickens.
05 - Adjust seasoning with salt and freshly ground black pepper to taste.
06 - In a large bowl, combine red cabbage, olive oil, apple cider vinegar, salt, black pepper, whole grain Dijon mustard, honey, and sugar. Mix well to coat cabbage evenly.
07 - Cover and refrigerate slaw overnight for optimal flavor and texture.
08 - Pile shredded honey mustard chicken onto sandwich rolls and top generously with prepared slaw before serving.