Baked Mushroom Thing

I have no idea what to call this but oooooh boy is it good. I came up with this trying to think of something that could be used as a main dish for a vegan style holiday meal and I think it turned out pretty good.  This is a multi-step recipe, but so worth it.

Served with Colcannon

1/2 to 3/4 c. Roasted Garlic and Basil Aioli
Extra virgin olive oil
1 large red onion, caramelized
1 puff pastry sheet rolled to about 1/4" thick
1 lb. mushrooms of mixed varieties, sliced (crimini/baby bella, button, portabello, etc.)
Sea salt
Black pepper
1-2 Tbsp. fresh thyme, roughly chopped
1 tsp. sherry vinegar or marsala wine vinegar
4 oz. tempeh, diced and browned in a little olive oil
1 Tbsp. soy milk 

1) Preheat the oven to 400 degrees. Heat a little olive oil over medium-high heat in a large saute pan and add the red onion and a sprinkling of sea salt. Give the onions a toss to coat and then leave them alone for about 10 minutes, until they start to brown. Once they start to brown toss them around and turn the heat down a little to medium. Let them sit for about another 5 minutes until they start getting evenly browned. Then continue to stir the onions until they are fully browned and caramelized.

2) As the onions are close to being done place the puff pastry shell on a sheet of parchment paper and roll it out a little with a rolling pin so that its about 1/4" thick and then move the parchment paper with the puff pastry still on it onto a baking sheet. Working lengthwise down the center, spread about 1/4 c. of the roasted garlic aioli along the length of the pastry.

3) When the onions have finished caramelizing spread them evenly down the center of the puff pastry atop the aioli.

4) Add a little more olive oil to the pan you used for the onions and add the mushrooms. Once the mushrooms start to brown (after about 5-7 minutes) add a little sea salt, the thyme and 1 tsp. sherry vinegar and toss around about 2-3 more minutes until they're cooked through. Then place the mushrooms over the caramelized onions.

5) In the same saute pan add a little more olive oil and the diced tempeh and cook while stirring occasionally until evenly browned, about 7 minutes. Then put the tempeh over the mushrooms.

6) Fold one end of the puff pastry sideways over the filling and then fold the opposing side over the first side so that you have a long log shaped item. Using a sharp knife with a wet blade (to avoid sticking), cut about 4 cross hatches on the top of the pastry to allow air to escape. Then brush a little soy milk over the top to aid in browning.

7) Bake for about 17-18 minutes until the pastry is nicely browned.

This serves 4 and is good with a little extra aioli and a sprig of fresh thyme on top.