These savory toasts are best with a mix of different mushrooms, so buy whatever varieties catch your eye — they're meant to be the star of the dish.

Ingredients

• 4 large egg yolks
• 1 tablespoon fresh lemon juice
• 1/2 tablespoon water
• 1/2 cup (1 stick) unsalted butter, melted
• hot sauce, to taste
• kosher salt, to taste
• freshly ground black pepper, to taste
• 5 cups assorted fresh mushrooms, such as sliced, stemmed shiitake, torn hen-of-the-woods, enoki, and morel
• 2 tablespoons vegetable oil
• 8 large eggs
• 1/4 cup whole milk
• kosher salt, to taste
• freshly ground black pepper, to taste
• 6 tablespoons unsalted butter, divided
• 4 (3/4-inch-thick) slices country sourdough bread
• 1/4 cup minced shallots
• 3 garlic cloves, grated
• 3 tablespoons white wine
• 1 tablespoon white soy sauce or regular soy sauce
• 12 ounces baby spinach
• 1/2 lemon, for squeezing over
• 4 ounces smoked gouda, coarsely grated
• 1/4 cup sliced fresh chives

Directions

1. In a large stainless steel bowl, whisk egg yolks, lemon juice, and water to blend. Place bowl over a saucepan containing barely simmering water (or use a double boiler). Continue to whisk rapidly until thickened, ensuring eggs don't get too hot or they will scramble. Remove bowl from over water and wrap bottom of bowl in a kitchen towel to keep it in place. Whisking constantly, slowly drizzle in melted butter until sauce is thickened and doubled in volume. Season to taste with hot sauce, salt, and pepper. Cover and place in a warm spot while cooking mushrooms and eggs.
2. Preheat oven to 375°F. In a large bowl, toss mushrooms and oil to coat. Spread out in an even layer on a large rimmed baking sheet. Roast until softened, 15 to 20 minutes.
3. In a medium bowl, beat eggs and milk until blended. Season with a generous pinch each of salt and pepper and set aside. Butter bread on both sides with about 4 tablespoons of the butter. Heat a large skillet over medium heat and add bread. Cook until golden brown, about 2 minutes per side.
4. In the same skillet, heat 2 tablespoons of oil over medium-high heat. Add shallots, garlic, and mushrooms and cook, stirring often, until shallots soften, about 4 minutes. Add white wine, 1 tablespoon butter, and soy sauce and bring to a simmer. Working in batches, add spinach, tossing until wilted between batches. Season with salt and a squeeze of lemon juice to taste.
5. In a non-stick skillet, melt 1 tablespoon butter. Add beaten eggs. Cook over medium heat, stirring with a silicone spatula, until eggs are just beginning to set, 2 to 3 minutes. Add smoked gouda, remove from heat, and continue stirring until eggs have just set into soft curds, returning to heat briefly if needed to cook slightly more, 1 to 2 minutes. Season with salt and pepper.
6. Spread hollandaise sauce on one side of each slice of toast. Top with sautéed mushroom and spinach, then scrambled eggs. Garnish with chives.