Heat a dry large skillet over medium heat. Add bacon; cook, stirring occasionally, until crisp, 5 to 7 minutes. Using a slotted spoon, transfer to a paper-towel-lined plate to drain. Add enough oil to bacon fat in skillet to total 2 tablespoons. Add garlic and Brussels sprouts; cook, stirring occasionally, until pale golden, about 3 minutes. Add stock; season with salt and pepper. Cook until most of the liquid has been absorbed and sprouts are tender, 5-7 minutes.