Scalloped Potatoes & Portobello Au Gratin

Thinly sliced potatoes, layered with sliced portobello mushrooms and cheese, all baked in creamy sauce.
Course Side Dish
Cuisine American
Keyword Au Gratin, Scalloped potatoes
Prep Time 10 minutes
Cook Time 1 hour 10 minutes
Total Time 1 hour 20 minutes
Author Lyuba Brooke


  • 2.5 lbs russet potatoes washed and peeled
  • 0.5 lb portobello mushrooms large
  • 1 1/2 cups shredded Mozzarella cheese
  • 6 oz sharp white cheddar cheese grated
  • Pint heavy whipping cream
  • 1/2 cup sour cream
  • 1/3 cup mayo
  • 3 cloves of garlic
  • 1 tsp thyme
  • Salt fresh cracked pepper


  1. Preheat oven to 350 and grease a 13×9 baking pan.
  2. In a mixing bowl, whisk together sour cream, mayo, heavy cream, pressed (or grated) garlic, salt and pepper.
  3. If you have a mandolin slicer, slice potatoes. (If you don't have one just slice them thin with a knife.) Slice mushrooms thin as well.
  4. Spread some of the cream sauce on the bottom of the baking dish and start layering half of the potatoes. Don't stack the potatoes but rather overlap if you have to.
  5. Spread half of mushrooms over potatoes, evenly. Spread half Mozzarella cheese and half of white cheddar cheese. Add some salt, pepper and thyme.
  6. Repeat the second layer: remaining potatoes, remaining mushrooms, remaining cheese.
  7. Pour cream sauce over the top, as evenly as possible.
  8. Bake for 60-70 minutes until all potatoes are done. You can stick a knife slowly in the middle and feel how easily it goes through the potatoes.

Recipe Notes

Recipe from Lyuba @ All images and content are copyright protected. Please do not use my images without prior permission. If you want to share this recipe, please simply link back to this post for the recipe. Thank you.