Combine soy sauce or tamari, ginger, garlic, jalapeño, and salt. Place in a 10" skillet and add 4 cups of water. Bring to a simmer over medium-high heat, and cook gently for 10 minutes.
Add the chicken. Cover the pan, and turn off the heat. Let the chicken sit for 5 minutes, then flip and let sit for another 5 minutes. If your chicken breasts are really big, and not quite cooked through, return the skillet to low heat and simmer the chicken for another 1-2 minutes.
Remove the chicken from the poaching liquid (save the liquid if you plan to have leftovers), slice and serve.