Heat a large skillet over moderate heat. Add oil, butter, garlic, and shallots. Gently saute shallots for 3 to 5 minutes to develop their sweetness. Add vodka to the pan, 3 turns around the pan in a steady stream will equal about 1 cup. Reduce vodka by half, this will take 2 or 3 minutes. Add chicken stock, tomatoes. Bring sauce to a bubble and reduce heat to simmer. Season with salt and pepper.