Parsnips With Spiced Peanuts and Garlic Yogurt

Name: Parsnips With Spiced Peanuts and Garlic Yogurt
Ingredients: 1½ lb. parsnips, peeled, trimmed, quartered lengthwise, cut into eighths if large; 2 Tbsp. unsalted butter, cut into pieces; 1½ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt, divided, plus more; 2 tsp. ground coriander, divided; ¾ cup salted, roasted peanuts, preferably cocktail, coarsely chopped; 1 tsp. crushed red pepper flakes; 1 tsp. ground cumin; 2 tsp. vegetable oil (optional); 2 tsp. sugar; Juice of ½ large lemon; 1 garlic clove, finely grated; ½ cup plain whole-milk Greek yogurt; 2 Tbsp. extra-virgin olive oil; Coarsely chopped parsley (for serving)