Preheat oven to 375°F (190°C). Butter a 9 in square (2.5 L) casserole dish and set aside. Bring a large pot of water to a boil. Cook pasta according to package instructions. Transfer to a colander, rinse under cold water and drain well.
In a large saucepan, melt 2 tbsp (30 mL) butter over medium-high heat. Add mushrooms and cook, stirring frequently, until tender, about 5 minutes. Transfer to a small plate and set aside. Wipe out saucepan, then return to stove and melt 3 tbsp (45 mL) butter over medium heat. Add flour and whisk constantly until bubbly but not brown, about 1 minute. Gradually whisk in milk, then wine and stock. Bring to a boil; reduce heat to medium low and stir constantly until thickened, about 4 minutes. Add 2 cups (500 mL) grated cheddar, Parmesan, thyme and pepper; stir until cheese is melted and sauce is smooth. Add chicken, pasta and mushrooms and stir well.
Pour into prepared dish and sprinkle with remaining 1 cup
(250 mL) grated cheddar. Cover loosely with foil (oiled to prevent sticking). Place on a baking sheet and bake until heated through, 20-25 minutes. Remove foil and sprinkle with potato chips. Continue to bake, uncovered, until top is golden and sauce is bubbly around the edges, about 15 minutes more.
In a serving: 792 calories, 52 g protein, 45 g fat, 45 g carbs
Note: Make ahead + freeze! Once the casserole is assembled, cool to room temperature. Cover tightly with aluminum foil and freeze up to 3 months. When ready to use, defrost in refrigerator overnight. Bake as below, adding more time if necessary.