Heat the canola oil in a large sauté pan over medium-high heat. Place the chicken skin-side down and sear for 5-6 minutes, until golden brown and crisp. Flip and sear the other side for 3-4 minutes, until cooked through. Transfer the chicken to a plate, cover loosely, and set aside.
Reduce the heat to medium and add the onion. Cook for 4-5 minutes, until softened. Add the garlic and cook for 30-60 seconds, until softened.
Pour in the white wine and deglaze the pan, scraping up the browned bits. Let the wine reduce until nearly evaporated.
Add the chicken stock, thyme, and parsley. Simmer until the liquid has reduced by about 75% and slightly thickened.
Whisk in the cold butter cubes, stir in the lemon juice, and season with salt to taste.
Return the chicken and any resting juices to the pan, skin-side up. Warm gently over medium-low heat, then serve with mashed potatoes and the pan sauce.