Mix yogurt with tandoori paste, lemon juice and mustard in a bowl. Season well with salt and pepper. Keep refrigerated until ready to use.
Wash the chicken breast, pat dry, and cut into bite-sized pieces.
Dip the chicken pieces into the yogurt mixture in batches, allowing excess to drain off, then place them directly into a plastic bag filled with breadcrumbs.
Close the bag and shake thoroughly so all chicken pieces are evenly coated with breadcrumbs.
Preheat the oven to 200°C (392°F) with top and bottom heat.
Place the coated chicken nuggets on a baking sheet lined with baking foil.
Bake for 20 minutes, turning the nuggets once halfway through (at 10 minutes). Chicken is done when the internal temperature reaches 74°C (165°F).