If speedy is what you're after, try tossing those chicken breasts in a pan (or a wok). Pan-frying, sautéing, and stir-frying all produce quick, tasty results in as little as 10 minutes -- that's total, not per side. It depends, of course, on the thickness of the chicken. A thicker breast may take up to 6 minutes per side; a pounded-thin breast might take about 4 to 5 minutes per side. Cut the chicken into bite-size pieces for the shortest cooking time of all.
This cooking method cuts down on total time in another way, too: You don't have to wait 10 minutes while the appliance preheats. It only takes about a minute to heat a pan to medium-high.
For one of the fastest chicken dinners you can make, cube a couple of chicken breasts and toss them in a pan or a wok with a bag of pre-washed broccoli or snow peas or a can of baby corn (or all three). Add bottled stir-fry sauce for the last 5 minutes of cooking. While you're stir-frying, boil a bag of quick rice. Dinner's on the table in about 15 minutes.
Finally, a method you may not have thought of ...