Preheat the oven to 365°F (convection/fan setting if available).

For the crust, blend olive oil, diced mozzarella, and one egg using an immersion blender until smooth and creamy. Transfer to a mixing bowl.

In a separate bowl, combine almond flour, flaxseed meal, salt, baking powder, and guar gum. Gradually stir the dry mixture into the mozzarella cream until a soft dough forms.

Let the dough rest for 5–10 minutes. Press it evenly into a 9.5–10 inch quiche pan or springform pan, pressing it up the sides. Line the bottom with parchment paper if desired.

Pre-bake the crust for 15 minutes, then remove from the oven.

Meanwhile, sauté the onion rings in olive oil over medium heat for 5–6 minutes until translucent. Add bacon and cook for 2–3 minutes.

Stir in leeks and mushrooms and cook for another 5–6 minutes. Remove from heat and allow to cool slightly.

Mix sour cream, whisked eggs, and grated cheese into the vegetable mixture. Season generously with salt and pepper.

Spread the filling evenly over the pre-baked crust.

Bake for an additional 30 minutes until set and lightly golden. Allow to rest briefly before slicing.