Breakfast Strata with Mushroom and Leeks

Close up of breakfast casserole with mushrooms and leeks with prosciutto on top

Our Breakfast Strata with Mushroom and Leeks is comforting, creamy and cheesy. Bonus points: it can be prepared the night before.

  • Author: Chef Sous Chef
  • Prep Time: 20 minutes
  • Cook Time: 1 hours
  • Total Time: 1 hour 20 minutes
  • Yield: 1 casserole 1x
  • Category: food and drink, brunch, main
  • Method: oven, stovetop
  • Cuisine: North American


  • 1/2 cup butter, divided
  • 2 large leeks, chopped*
  • 2 cloves garlic, minced 
  • 250g mushrooms, chopped*  
  • 10 eggs
  • 3 cups milk
  • 1 tsp dry mustard
  • 1 loaf sourdough bread, cubed
  • 250g medium cheddar cheese, grated
  • 1 tsp fresh thyme
  • 100g prosciutto, very thinly sliced
  • 1 tsp salt
  • 1/2 tsp pepper


No. 1 | Melt 1 tablespoon of butter in a skillet on medium-high heat. Add the leeks and season with a pinch of salt and pepper. Sauté for 3 minutes, stirring often, until softened. Transfer to a bowl and return the skillet to the stove. Melt another tablespoon of butter and add the garlic. Cook for 30 seconds, then add the chopped mushrooms. Season with salt and pepper and cook for 5 minutes, until they just start to soften. They do not need to be cooked entirely through. Transfer them to a separate bowl. 


No. 2 | In a large bowl, whisk together the eggs, milk, dry mustard and 1/2 teaspoon of each salt and pepper. 


No. 3 | Place the bread cubes in a casserole dish or roaster. Add half of each the leeks, mushrooms, and cheese plus 1 teaspoon of thyme. Toss together until all the ingredients are evenly incorporated. Pour the egg mixture over the bread, ensuring that every bread cube gets soaked. Sprinkle remaining leeks, mushrooms, and cheese on top. Set aside to allow the bread to soak up the eggs, while you heat the oven. 


No. 4 | Preheat oven to 350°F. Tear the prosciutto and arrange throughout the strata, tucking it into the nooks and crannies of the bread cubes. Once the oven is preheated, melt and drizzle remaining butter evenly over the strata. Place in the oven to bake for 1 hour, or until golden brown on top and the eggs have set. 


  • Only the very light green and white parts of the leek are edible. Cut off the tough, darker green portions of the leeks. Leeks are also usually very dirty. To clean, slice the leeks and transfer to a large bowl of water. Shake and grate the leeks with your finger tips, then transfer to a sieve set over a bowl. Use your hands to do this, otherwise you will end up pouring the dirt back in. Do this a second time if necessary.
  • A mix of mushrooms produce wonderful results. We used an equal combination of cremini, portabello, oyster, and shiitake mushrooms for this recipe. 
  • This is a great make ahead recipe. Follow steps 1-3 then place the strata, covered in the fridge overnight. Remove from your refrigerator 20 minutes before baking.

Keywords: breakfast casserole, strata recipe, easy holiday recipes, brunch recipes