Vegetarian Shepherd's Pie Topped with Buttery Potatoes!

Ingredients

• 2 large russet potatoes (peeled and quartered)
• ½ cup non-fat Greek yogurt
• 3 tablespoons unsalted butter
• ½ teaspoon salt
• ¼ teaspoon black pepper
• 3 tablespoons olive oil
• 1 medium onion (diced)
• 16 ounces mushrooms (chopped)
• 2 carrots (peeled and diced)
• 2 garlic cloves (minced)
• 1 tablespoon fresh thyme (plus more for serving)
• 2 tablespoons uncooked quinoa
• 2 tablespoons tomato paste
• 1 teaspoon salt
• 1 ¼ cup vegetable broth
• 1 cup frozen peas
• Chopped parsley (for serving)