Vegan Chicken Tetrazzini

Total time1 hr 5 min

Prep time20 min

Cook time45 min

Cozy, creamy, and utterly satisfying, this baked pasta casserole layers tender spaghetti with sautéed leeks and earthy cremini mushrooms in a thick, velvety sauce built up with a classic roux technique. Sweet green peas and fresh parsley brighten every forkful, while a golden, crumb-topped crust forms as it bakes uncovered until bubbling at the edges. It's the kind of dish that fills the kitchen with the smell of a Sunday night dinner, with a hearty texture that makes it feel indulgent even though it's really just pantry staples done right. Scoop it straight from the baking dish while the top is still crackly-crisp for the best contrast against that rich, saucy interior. This one holds up beautifully as a make-ahead casserole, and it's a genuinely solid choice for a vegan spread without sacrificing any of that comforting, old-school tetrazzini feel.

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Ingredients

6 servings

For the pasta

12 oz spaghetti
Wild Harvest Spaghetti, Corn & Rice Blend, Gluten Free 12 Oz De Cecco Organic Spaghetti - 12 Oz Wild Harvest Spaghetti, Organic, Whole Wheat 12 Oz Organic Gluten Free Brown Rice Spaghetti, 12 oz Natural Grocers Organic Spaghetti, 12 oz
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For the chicken

1 ½ lb boneless, skinless chicken breasts
Chef's tip
Choose an unbreaded plant-based cutlet and cook it according to its package - ignore the recipe's raw-chicken cooking times and temperatures - then use it where the cooked chicken goes.
1 tbsp olive oil
½ tsp salt

For the sauce

4 tbsp unsalted butter
Chef's tip
Use a stick or block-style dairy-free butter - not a soft tub spread - and swap one-for-one.
2 medium leeks, white and light green parts only, thinly sliced
10 oz cremini mushrooms, sliced
¼ cup all-purpose flour
2 ½ cups low-sodium chicken broth
Chef's tip
Use the same amount of low-sodium vegetable broth. The dish will be a little lighter in flavor than with chicken broth.
1 cup whole milk
Chef's tip
Use plain, unsweetened oat milk, measured 1:1. It works well in drinks, batters, sauces, and soups; avoid it where milk sets the texture, like custards, puddings, and frozen desserts.
½ tsp dried thyme
½ tsp salt
½ cup frozen peas
2 tbsp fresh flat-leaf parsley, finely chopped

For the topping

½ cup grated parmesan cheese
Chef's tip
Choose a grated-style vegan parmesan and use the same amount.
½ cup plain breadcrumbs
1 tbsp unsalted butter, melted
Chef's tip
Use a stick or block-style dairy-free butter - not a soft tub spread - and swap one-for-one.

Instructions

1
Preheat the oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish and set aside.
2
Bring a large pot of salted water to a boil. Cook the spaghetti until just shy of al dente — tender but with a firm, chalky center — about 1 minute less than the package directions. Drain in a colander and set aside.

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