Ingredients:

  • 1 Tbsp (15 ml) Unsalted Butter or Olive Oil
  • 1 medium Yellow Onion, finely chopped (approx. 100g)
  • 225g (8 oz) Cremini Mushrooms, sliced
  • 280g (10 oz) Fresh Spinach, washed and thoroughly dried
  • ½ tsp Kosher Salt (for vegetables)
  • ¼ tsp Black Pepper, freshly ground (for vegetables)
  • 6 large Eggs
  • 120 ml (½ cup) Whole Milk
  • 120 ml (½ cup) Double Cream (Heavy Cream)
  • 150g (5 oz) Gruyère Cheese, grated
  • ½ tsp Dijon Mustard
  • ¼ tsp Ground Nutmeg
  • ½ tsp Kosher Salt (for custard)
  • ¼ tsp Black Pepper (for custard)
  • 1 Tbsp Soft Butter (for greasing)
  • 1 Tbsp All-purpose Flour or fine Breadcrumbs (for dusting)

Instructions:

  1. Preheat the oven to 180°C (350°F). Place an oven rack in the centre position. Prepare the 9-inch pie dish: Grease the entire interior thoroughly with soft butter, then dust generously with flour or breadcrumbs (this non-stick barrier is crucial for a crustless quiche). Shake out any excess.
  2. Heat the butter or oil in a sauté pan over medium heat. Add the chopped onion and cook until softened (about 4–5 minutes). Add the sliced mushrooms and cook until all liquid has evaporated and they begin to brown slightly (approx. 8–10 minutes).
  3. Add the spinach to the pan and cook until just wilted (1–2 minutes). Season the vegetables with the initial salt and pepper. Remove from heat and set aside to cool slightly.
  4. In a large mixing bowl, whisk the 6 large eggs vigorously until slightly frothy. Slowly whisk in the whole milk and double cream until just combined. Stir in the Dijon mustard, nutmeg, the remaining salt, and pepper.
  5. Fold three-quarters of the grated Gruyère cheese into the custard mixture.
  6. Scatter the cooled vegetable mixture evenly across the base of the prepared pie dish. Pour the egg custard slowly and evenly over the vegetables. Sprinkle the remaining Gruyère cheese over the top.
  7. Bake for 40–45 minutes, or until the edges are set and golden, and the centre has a slight gentle jiggle. If the top browns too quickly, loosely tent the dish with foil.
  8. Remove the quiche from the oven and allow it to rest for at least 10 minutes before slicing and serving. This resting period ensures the internal structure is firm and prevents a runny centre.