I’m a fan of onion in every form. Before keto, panini with caramelized onion and cheese was one of my guilty pleasures. I love the sweetness of onion fried with butter or grilled sprinkled with salt that balance the sweetness. The same with mushrooms fried with butter on high heat when they get golden brown but still firm. I feel like butter can boost flavour of everything. There is a quote: “the only thing better than butter is more butter” and that’s absolutely the truth 🙂 But I mean real butter, not the spread or margarine. Real butter with at least 80% of fat (the best grass fed). I feel like I could write separate post about butter but lets focus on the tart.
Although preparing of this tart might seem to be complicated it’s actually very easy. If you want to prepare it with regular crust, you can prepare it yourself, or buy ready made shortcrust pastry (already rolled). Of course I recommend making it at home (with butter, not margarine that’s used in ready made pastry), but if you don’t have enough time or skills, this option is fine as well.
I’ve prepared this recipe for both options: regular and keto / gluten free. Choose whatever is best for you. Inspiration for the tart comes from here, with my adjustments. I used this recipe as a base for keto crust.
It’s great keto meal, full of fat and very fulfilling – this keto crust is mostly fiber, so will make you feel full for hours even though it’s not heavy and doesn’t contain any meat. But of course you could feel temptation to toss some fried bacon on top…
mushroom and onion tart
NOTE: my measuring cup is 250ml regular glass
INGREDIENTS for regular crust:
- 1 cup plain flour
- about 80g butter
- 2 tbsp very cold water
INGREDIENTS for keto crust:
- 1 cup ground linseed (flaxseed)
- 1/3 cup coconut flour
- 1/4 tsp natural rock salt
- 1/2 tsp baking powder
- 2-3 tbsp clarified butter (or coconut oil)
- 1 egg
- 2 tbsp milk (I used almond milk)
INGREDIENTS for stuffing:
- 2-3 red onions
- 2-3 white onions
- about 500g mushrooms
- 3 tbsp olive oil / coconut oil / clarified butter
- 2 tbsp balsamic vinegar
- slice of butter
- natural rock salt and coarse pepper to taste
- 1 large egg
- 200g cream cheese (for example ricotta or philadelphia)
- 1 cup grated mature cheddar
- ½ cup double cream
- handful of chopped spring onion
DIRECTIONS for regular crust
Chop the butter with flour, add 2 tbsp of very cold water and knead quickly to a uniform dough. Form into a ball, wrap in plastic and put to the fridge while you prepare the rest of ingredients.
DIRECTIONS for keto crust
I use old coffee grinder to grind linseed, you can do the same, or buy grounded linseed. Although it’s more expensive and less healthy, because ground linseed oxidize quickly. That’s why it’s better to buy linseed and grind only the amount you need. You can also use mortar to grind them, but it’s more time consuming and requires more attention.
In a bowl mix together grounded linseed, coconut flour, salt, baking powder, butter, egg and milk using your hand. Form into a ball, wrap in plastic and put to fridge while you prepare the rest of ingredients.
DIRECTIONS for stuffing and baking
In a big skillet heat olive oil / coconut oil / butter. Peel onions and cut in quarters, fry on a medium heat, season with salt and balsamic vinegar. Fry until golden and and slightly tender but still firm. Transfer them to a bowl and use the same skillet for frying mushrooms. Depending of size chop them in quarters or slices. Fry quickly on high heat until golden. Add some salt at the end of frying (adding salt at the end will prevent from becoming soggy).
Roll the dough to a circle (with regular dough you”l need slightly floured surface), gently transfer to a tart baking dish. Don’t worry if it breaks while transferring , just use your fingers to put everything back together. Pierce bottom with a fork and return to fridge for 20 to 30 minutes.
Heat the oven to 180-190ºC (no fan). Bake the crust for about 15 minutes.
In the meantime separate egg yolk and egg white. Mix egg yolk with cream cheese and half of grated cheddar. In a bowl whip egg white, add double cream and remaining cheddar.
Take the crust from the oven, spread the mix of cream cheese on the bottom, then place mushrooms and onions, and pour the mix of egg white, double cream and cheddar.
Cover with foil (shiny side is from the inside, dull outside) – it will prevent from burning and bake for about 30 minutes. Then take of the foil and bake couple more minutes until golden. Your tart is ready – just sprinkle with chopped spring onion.
In my opinion the best is next day or after couple hours, when the crust gets moist with the juices from mushrooms and onion.