As you already know chicken breast "braised" in liquid, soup etc can be very tough and rubbery. A quick idea would be 1. Use dark meat as in thighs that do cook tender in liquids. 2. Briefly cook(saute) the breast meat in butter,evoo or a combination of the two then add to your Mulligatawny. The key word is "briefly" do not over cook. I hope this helps...
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