Heat a large skillet with olive oil. Cook the minced onion and garlic for about 3 minutes until translucent. Add the finely chopped mushrooms and cook for about 5 minutes on high heat, until no liquid is left.
Add the lemon juice, fresh herbs, and spices and stir well. Transfer into a bowl and let it cool entirely. *Can be made one day ahead and stored in the fridge.
Marinate Beetroot
Place the cooked beetroots, mustard, salt and pepper in a bowl. Massage using your hands until the beets are well covered.
Assemble Beet Wellington
Preheat the oven to 390°F/200°C.
Two Small Beet Wellingtons (see notes): Cut the puff pastry in half. Lay it with the shorter side ahead of you on a parchment paper (easier to transfer later).
Place ¼ of the mushroom duxelles into the middle of the puff pastry. Lay half of the beetroots on top (you might need to cut one beetroot in half to divide them equally between the two small wellingtons). Place ¼ of the mushroom duxelles on top and around the beets, it's the easiest to do this using your hands and slightly press the mushrooms to stick on the beets.
Cut the remaining puff pastry in long strips and lay them on top of the beetroots (it's a little bit like braiding) and transfer onto a baking sheet. -> Check out the step-by-step images in the blog post above. So much easier to make when you see it.
Repeat with the second half of the puff pastry.
One Big Beet Wellington: Lay the whole puff pastry sheet with the shorter side ahead of you on a parchment paper. Proceed the same way as above explained.
Brush the puff pastry with plant-based milk and bake for 25 minutes in the preheated oven until golden brown.
You can make one large or two small beet wellingtons. I prefer the second option as it’s easier to handle and you can leave one in the oven to stay warm.
I always use storebought cooked beetroot in natural juice. It’s the fastest way, and you don’t have to deal with purple hands & kitchen. Make sure all are about equal in size.
Most puff pastries are vegan, but make sure and check the label before buying it.