Buffalo Chicken-Stuffed Peppers

Preheat oven to 400°. Place bell peppers cut side up on a large baking sheet and drizzle all over with olive oil, then season with salt and pepper. In a large skillet over medium heat, melt butter. Add onion and cook until tender, about 5 minutes. Add garlic and cook until fragrant, 1 minute more. Add shredded chicken and hot sauce and toss until combined. Cook until the mixture comes to a simmer, then remove from heat. Divide chicken mixture between pepper halves. Top with Gouda and bake until cheese is melted and peppers are crisp-tender, 20 to 25 minutes. Drizzle each stuffed pepper with ranch dressing and sprinkle with chives.