Preparation

1. Preheat the oven to 375°F (190°C).
2. Butter a 2-quart baking dish or a deep 9-inch ovenproof skillet.

Pasta Cooking

1. Cook the linguine according to package directions until al dente. Drain and transfer the pasta to a large bowl.
2. Toss with butter and allow it to cool to almost room temperature.

Onion Sauté

1. In a skillet, melt a tablespoon of butter over medium heat.
2. Add the finely diced onions and sauté until translucent and slightly caramelized, about 5-7 minutes.

Mixing the Ingredients

1. To the cooled pasta, add the sautéed onions, chopped burrata cheese, whole-milk ricotta, grated Parmigiano Reggiano, chopped parsley, and chopped chives.
2. In a separate bowl, lightly beat the two eggs and then add them to the pasta mixture.
3. Mix everything thoroughly.

Baking

1. Transfer the mixed ingredients into the prepared baking dish or skillet.
2. Bake in the preheated oven for about 25-30 minutes, or until the top turns a golden brown and the edges are crispy.

Finishing Touch

1. Remove the dish from the oven and immediately sprinkle freshly ground black pepper on top.
2. Allow the linguine pie to rest for about 30 minutes to set.

Serving

1. Cut the linguine pie into wedges and serve.