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top down view of finished asparagus casserole

Asparagus Casserole

Asparagus Casserole has tender asparagus and mushrooms baked in a luscious Dijon cream sauce. This festive and colorful side dish is a variation of asparagus au gratin and perfect for a special dinner.
5 from 6 votes
Prep Time 5 mins
Cook Time 40 mins
Total Time 45 mins
Course Side Dish
Cuisine American
Servings 4 people
Calories 300 kcal


  • 1-½ lb fresh asparagus spears see Notes
  • 1-½ Tbsp extra virgin olive oil divided (plus ½ tsp for the topping)
  • 8 oz baby portabello mushrooms sliced
  • ½ medium white onion diced
  • ½ cup heavy cream
  • 1 cup half and half
  • 1 Tbsp whole grain mustard
  • 1 Tbsp Dijon mustard
  • ½ tsp kosher salt
  • good pinch fresh cracked pepper
  • 2 Tbsp panko breadcrumbs
  • 1 Tbsp freshly grated Parmigiano-Reggiano cheese
  • garnish: fresh chopped basil leaves


  • Heat oven to 400°F.
  • Blanch the asparagus in boiling water and transfer immediately to ice water to stop the cooking. If asparagus spears are thin, blanch 1 minute. If they are thick, blanch 2 minutes. Drain completely.
  • Heat 1 tablespoon olive oil in a medium saucepan over high heat. Add the mushrooms and cook, tossing occasionally, until mushrooms are well browned.
  • Add half a tablespoon olive oil and the onion to the mushrooms. Cook, tossing occasionally, until onion is lightly browned. Remove from the heat and set aside.
  • In a clean, medium skillet, heat the cream and half and half over medium heat until bubbly. Simmer gently 10 minutes to thicken. Whisk in the whole grain and Dijon mustard, salt, and pepper. Remove from the heat.
  • In a mixing bowl, combine the asparagus, mushroom-onion mixture, and Dijon cream. Transfer to a 2-qt casserole dish or equivalent.
  • In a small bowl, combine 1/2 teaspoon olive oil, panko breadcrumbs, and parmesan cheese. Sprinkle over the asparagus casserole.
  • Bake at 400°F for 20-30 minutes until bubbly and golden on top, and asparagus is fork tender.


If the asparagus spears are thicker, the stems will be "woodier", and there will be less asparagus after trimming. Therefore, if spears are standard, 1-1/2 lbs will suffice. If spears are larger and thicker, getting 2 lbs will allow for the loss to trimming. Either way, you want to end up with 1 lb asparagus to cook after trimming.
See the body of the post for important tips not included in the recipe card.


Calories: 300kcal (15%)

Calorie count is purely an estimate calculated using an online application to serve as a guide and not to be taken as accurate nutritional information. Percent Daily Values are based on a 2,000 calorie diet.

Keyword asparagus casserole, asparagus gratin
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