He simply watched her, wanting to be encouraging and also secretly admiring her full and curvaceous figure now that she'd had some food in her. His cheek rested on his hand who's elbow rested on the table, and he almost lost himself in his male gaze before he saw the potato slip. By the Lord, he was proud of her for even asking to learn, so he wouldn't let her lose courage now of all times. 

He pushed himself up, and drew in closer to her. He grabbed the potato, his chest pressing to her back and her head as he guided her hand with the knife back to the potato. "Here, hold it firmly like this." He said to her, his large hands over hers as the potato was held in place. "We don't need the potatoes sliced too thinly. Just..." He cut the potato with her hand, guiding her along. "Thin enough. See?"