Garlic Vegetable Casserole Recipe

Preheat and prep

Preheat oven to 375°F (190°C). Lightly grease a 9x9-inch (or similar) casserole dish.

Trim and cut broccoli and cauliflower into bite-sized florets. Peel and slice carrots; dice the red pepper; slice the onion thinly; cut zucchini into half-moons. Aim for relatively uniform pieces so they cook evenly.

Bring a large pot of salted water to a boil. Blanch the broccoli and cauliflower for 2 minutes, then add the carrots and blanch everything together 1 additional minute. Immediately transfer vegetables to an ice bath to stop cooking, then drain thoroughly. (Zucchini and bell pepper should not be blanched; they will be added raw in the casserole).

Mince the garlic and chop the thyme and parsley if using fresh. Set aside.

In a large skillet over medium heat, warm 1 tablespoon olive oil and the butter until butter melts and foams. Add the sliced onion and sauté 4–5 minutes until soft and translucent, stirring occasionally.

Add the minced garlic and thyme to the skillet and cook 30–45 seconds until fragrant, taking care not to brown the garlic.

Stir the flour into the onion-garlic mixture and cook 1 minute to eliminate the raw flour taste.

Gradually whisk in the vegetable broth until smooth, then whisk in the half-and-half. Increase heat to medium-high and bring to a gentle simmer, whisking, until sauce thickens slightly (about 2–3 minutes).

Lower heat to medium, whisk in the 3 tablespoons grated Parmesan and Dijon mustard until incorporated. Season sauce with 1 teaspoon kosher salt and 1/2 teaspoon black pepper; taste and adjust seasoning. If sauce becomes too thick, thin with up to 2 tablespoons more broth or milk.

Combine the blanched broccoli and cauliflower, raw carrots (if you left some raw), diced red bell pepper, zucchini, and most of the chopped parsley in a large bowl. Pour the warm garlic cream sauce over the vegetables and toss gently to coat evenly.

Transfer the sauced vegetables into the prepared casserole dish, spreading them into an even layer.

In a small bowl, mix panko breadcrumbs with the 2 tablespoons extra Parmesan, 1 teaspoon olive oil, remaining 1/2 teaspoon kosher salt, 1/2 teaspoon black pepper, and red pepper flakes if using. Sprinkle the breadcrumb mixture evenly over the casserole.

Bake uncovered in the preheated oven for 20–25 minutes, or until the topping is golden and the casserole is bubbling around the edges. If you prefer a more browned top, switch oven to broil for the final 1–2 minutes—watch closely to avoid burning.

Remove casserole from oven and let rest 5–7 minutes. Sprinkle with remaining parsley before serving.