1. Heat oils in a large skillet over medium-high heat.
2. Once hot, add the brussel sprouts and shallots, and sauté until browned, about 5-6 minutes.
3. Deglaze the skillet with the apple cider, bring to a simmer, and cook, stirring occasionally, until the sprouts are tender-crisp and the cider has reduced by half, about 5 minutes more.
4. Transfer the brussel sprouts and shallots to a serving platter and top with flaked sardines, walnuts, and parsley.
5. Season to taste with salt and pepper before serving.