MIX mustard and dressing with wire whisk until well blended; cover. Refrigerate until ready to use.
FOR each serving: Spread each cut side of croissant with 1 Tbsp. of the mustard mixture. Place 1 lettuce leaf, 2 process cheese slices, 4 ham slices, 2 turkey slices and 2 pepper strips on bottom half of croissant; cover with top half of croissant.