HEAT 2 Tbsp. of the dressing in extra-large skillet or Dutch oven on medium-high heat. Add chicken, skin-sides down, and onions. Cook 4 min. on each side or until chicken is browned on both sides, stirring onions occasionally. Cover. Reduce heat to medium-low; simmer 15 min. Add remaining dressing and the boiling water; cover. Simmer an additional 15 min.; strain. Chop the chicken; discard skin and bones. Return the chopped chicken and strained liquid to skillet.

SIFT flour, baking powder and salt into large bowl. Cut in shortening with pastry blender or two knives until mixture resembles coarse crumbs. Add milk; stir until mixture forms a stiff dough. Place on lightly floured surface; knead 8 to 10 times or until smooth. Roll out dough to 1/4-inch thickness; cut into 1-inch squares.

ADD dumplings to the boiling soup; cover skillet with lid. Reduce heat to medium-low; simmer 40 min. or until dumplings are cooked through.