Chicken and marinade: add brown sugar, pepper, five spice powder, sesame oil, soy sauce, fish sauce, honey, minced garlic, and minced shallot to a medium-sized bowl and whisk to combine. Add your pieces of chicken and allow everything to marinate overnight or for at least 4 hours.

When you are ready to cook, heat a large dutch oven or pot with a lid on high with 2 tablespoons of oil. 

When the oil is hot and shimmering, carefully add each piece of chicken and sear for 3 minutes on the first side and then flip and sear for another 3 minutes. Do not discard the leftover marinade.

After six minutes of cooking, pour in the leftover marinade, reduce heat to low, cover the pot with a lid, and cook for 10 minutes. 

Remove the lid, raise the heat back up to medium, and cook for another 5 minutes with the lid off. After five minutes as elapsed, remove the chicken to a plate or cutting board to rest before slicing.

Pickled veggies: julienne the carrots and daikon radish, slicing them into planks, and then matchstick shapes. 

In a small pot over medium heat, add the rice vinegar, water, sugar, and salt. This is your pickle brining liquid. Bring it to a boil and then remove the pot from the heat. 

Add the carrots and daikon radish to a container and pour over the pickle brine. Store these in a covered container in the refrigerator overnight. 

Sandwich assembly: when it's sandwich time, combine 3 tablespoons of mayonnaise with the sriracha and oyster sauce to create a slightly spicy sandwich sauce.

Slice your croissant and toast if desired. Spread the mayonnaise and sriracha sauce into the interior of the bread.

Add slices of chicken on top of the sauce. Next, add thin slices of cucumbers and jalapenos. Top with pickled carrots and daikon radish and cilantro leaves. 

Top the sandwiches with more sauce if desired. Serve and enjoy.