Warm the oil in a large skillet set over medium-high heat, then add the garlic and cook for a few minutes. Add the chard stalks, cover, and reduce the heat to low. Cook until the stalks are quite tender, about 30 minutes. Remove from heat and let cool slightly.
Add the yogurt, tahini, lemon juice, and salt. Mix well, transfer to a serving dish, and garnish with pomegranate seeds, if usi