Season chicken generously with salt and pepper. This is your first tiny victory of the night.
Heat olive oil in a skillet over medium-high heat. Sear the chicken until golden, about 3–4 minutes per side. Remove and set aside; you’ll finish it off later.
In the same pan, sauté the onion until soft and translucent. Add garlic and cook 30 seconds more—don’t burn it, or it’ll taste like the gym you forgot to visit.
Pour in the Riesling to deglaze the pan, scraping up all the tasty brown bits. Let it simmer for 2–3 minutes to reduce a bit.
Add chicken broth, lemon juice, and Dijon mustard. Stir, then bring to a gentle simmer.
Return chicken to the pan. Simmer for 6–8 minutes, until the chicken is cooked through and the sauce has slightly thickened.
Stir in the heavy cream and butter. Cook for another 2–3 minutes until glossy. Taste and adjust seasoning with salt and pepper.
Finish with chopped parsley or thyme. Plate, spoon generous sauce over the chicken, and go selfie-mode, you earned it.