Add olive oil and leeks to a pan and cook gently for about 10 minutes on medium heat. Watch them carefully; they should soften but not get brown. They turn bitter when burned.
Add garlic and cook gently for another ten minutes.
Now it is time to add the wild garlic and let it wilt for about 5 minutes. Make sure everything is soft before you turn the heat off and move the pan off the hot plate.
Make the cheese sauce by blending water, cashews, salt, nutmeg, lemon juice and nutritional yeast in a blender and transfer to a saucepan. Cook over medium heat and stir constantly. It will thicken within 2 - 5 mins.
Add the xanthan gum and continue stirring for another minute. You can find xanthan gum in the baking aisle of any well-stocked supermarket. It is needed to give the mass a stretchy and cheesy consistency.
Pour the cheese sauce onto the cooked vegetable mixture and stir until evenly combined. Set it aside and let it cool down.
Meanwhile, prepare the puff pastry. It can be bought both in a block or already rolled out. If you buy it in a block roll it out very thinly. About 3mm (1/10 inch).
Take your quiche forms*(see notes) and cut circles out by pressing them into the puff pastry sheet. Line your forms with the puff pastry and gently press it down. The edge does not have to be significantly high since the filling is not runny. One 1 cm (1/2 inch) is more than plenty.
Fill each quiche with about 1 heaped tbsp of the cheesy vegetable mass and spread it evenly. Make sure to keep it thin. Not more than twice the thickness of the puff pastry. Sprinkle the quiches with a dash of salt and pepper.
Bake them in a preheated oven at 180°C / 350°F for 20 mins until the puff pastry turns golden brown.
Serve immediately while still warm and sprinkle with some freshly chopped wild garlic if you want.