Mix the macaroni, chicken stock, salt, pepper, and garlic powder in the Instant Pot. Close and lock the lid. Set to manual/pressure cook and set the time for 5 minutes and press start.

While the macaroni is cooking, heat a sauté over medium heat and add olive oil. Once the oil is hot, add mushroom and thyme and cook for about 8 minutes until mushrooms are browned.

Once the Instant Pot is finished, quick release the steam, drain noodles, and return to pot. Add milk, butter, and cheese until melted and the macaroni is well coated. Stir in mushrooms and tomatoes. Pour the macaroni mixture into a baking dish and add the Panko bread crumbs over the top. Broil until the Panko is browned, will only take a few minutes (be careful, the Panko will burn very quickly so keep a close eye on it). Top with parsley.