In a large-bowl, mix all the ingredients to the chicken & marinade then coat the chicken nicely. Put aside and simmer for 30 minutes, or overnight.
Next, in a large skillet over medium-high-heat, heat 1 tbsp cooking-oil & transfer the chicken and marinade to the skillet. Then putting the chicken thighs flat side-down
Let cook without disturbing for 5minutes then flip and cook for another 5-8minutes on this side, then flip once again. Reduce the heat a little (the sauce ought to be thicker at this stage).
Utilize your spatula or tongs to move the thighs around to coat them at the rest of the sauce in the pan during the last couple of minutes of cooking. After cooked through, remove from heat.
In the same skillet, then add another tbsp of cooking-oil then stir in with the rest of the sauce which was left from the skillet to include.
Add the green-beans, tossing them from the pan with the mustard powder, red pepper flakes and salt.
Cook them till they achieve your preferred softness, tossing or stirring often (3-minutes for crisp and 10-minutes for very soft). Add additional oil if necessary while cooking.
Serve and enjoy!