In a medium bowl, whisk together 1/2 cup of Water, 1/2 cup of Rice Vinegar, 1/3 cup Dark Brown Sugar, and 1 1/2 tsp Salt. Add sliced Cucumber and 1 1/4 cup shredded Carrots. Cover and allow to soak for at least 30 minutes in the refrigerator.
When ready to cook the chicken, whisk together 1 tbsp Dark Brown Sugar, 1 tbsp Sriracha, 1 tbsp Rice Vinegar, 1 tbsp Fish Sauce, 1 tbsp Ginger, 1/4 cup Soy Sauce plus 2 tbsps of water. Set aside.
On one cutting board: chop the Yellow Onion into quarters, slice the Jalapeno, and cut off 1/2 bunch of Cilantro. Set aside.
Heat the Instant Pot on the Saute setting. Add a swish of oil (Canola, Vegetable, or Olive will do).
While the Instant Pot heats up, season the Chicken with Salt and Pepper.
In the now hot Instant Pot, add the seasoned Chicken and sear for one minute on each side.
Remove the Chicken to a plate. Add the Quartered Onion, Sliced Jalapeno, minced Garlic and Cilantro to the Instant Pot. Cook for 2 minutes, stirring constantly to avoid sticking.
Add Chicken back into the Instant Pot. Pour the prepared mixture from step 2 on top of the Chicken. Cover and pressure cook on the 'chicken setting' for 8-10 minutes depending on the size of the Chicken.
Once the Chicken is almost done, preheat the oven to the 'broiler' setting. Line a baking sheet with foil.
Perform a 'quick release' once the time is up. Remove the Chicken to a cutting board and shred using 2 forks.
Spread the Chicken on the baking sheet. Drizzle 1/4 cup of the cooking liquid remaining in the Instant Pot over the Chicken along with a tbsp of Sesame Oil and toss together.
Broil the Chicken for 10 minutes stopping halfway to toss the Chicken with 2 more tbsps of the cooking liquid.
To assemble: spread Sriracha Mayo on a toasted baguette, add cilantro and sliced Jalapeno to the spread mayo (this helps them stay in place on the baguette). Next, add the pickled Cucumber slices and shredded Carrots. Finally, add the shredded Chicken.