WHAT YOU'LL NEED
1 sheet puff pastry, defrosted but very cold
1 delicata squash
4 tsp olive oil, divided
1 tsp dijon mustard
1 large sweet yellow onion
4 Tbs sherry or preferred wine, or broth
3 oz crumbled gorgonzola
1 Tbs honey (I used smoked, but regular is great too)
1 Tbs pine nuts, toasted
3 sprigs fresh thyme, plus more for garnish if desired
1 egg whisked with 1 Tbs milk or water for egg wash (for color, optional)
WHAT YOU'LL DO
First, caramelize the onions.
This will be the most time consuming part, so note that they can easily be done ahead of time, the day before even, and stored in an airtight container.
Peel and slice your onion in half-moon shapes about 1/8 thick. Preheat an 11 or 12 inch skillet on medium-low heat and add 2 tsp of your olive oil to the pan. Add in your onions, and cook them, NEVER turning your heat above medium/low. I know this is hard to do, but if your heat is too high, the onions will never caramelize, they will just burn. Keep the lid partially on or cracked, so air can pass through, and stir the onions every 4-5 minutes. This process will take about 40-45 minutes, and there really are no shortcuts. So put on a show, have a glass of wine, or waste time on your phone nearby while you wait for them to do their thing. After they are considerably reduced, softened, and a rich, reddish brown, you are ready to deglaze your pan. I used Sherry cooking wine but you can use any wine you’d like to flavor them with, or even broth. Add in the sherry or broth, one Tbs at a time (total of 4) and stir the onions, scraping up the bottom of the pan as you do. Of course, deglazing your pan is optional, but I personally think at this point you’ve come to far to skip this step. Not only is it a great way to get your pan clean from all those browned bits, it will give the onions incredible flavor. Once you are done, set your onion candy aside to cool or store it for later.
FOR THE TART:
First, preheat your oven to 375 degrees Fahrenheit.
Wash your delicata squash well (since the skin is edible and you won’t be peeling it) and slice it in half lengthwise. De-seed it, and slice 1/4 inch thick slices. Toss in a bowl with remaining 2 tsp olive oil, a pinch each salt & pepper, and 1 tsp of dijon mustard, until evenly coating the squash slices. Spread out evenly on a baking sheet and bake, for 15-20 mins until fork tender but not mushy.
Meanwhile, lightly flour a work surface and roll out the puff pastry until it is as close to a 12 x 14 inch rectangle as you can get it. Trim uneven edges, and then lightly score (without cutting all the way through) the edge 1/2 inch in from the border all the way around with a knife to make a crust edge. Prick the puff pastry all over within that border with a fork and transfer to a baking sheet lined with parchment paper. Bake at the same temp as the squash, about 15-20 minutes until starting to turn a light golden color. Remove from the oven, and let cool for a few minutes while you gather all your toppings.
Now, for assembling the tart. Brush the cooling puff pastry all over with the egg wash, especially heavier on the border. Spread your caramelized onions in a single layer within the border, then top with roasted delicata squash slices in whatever pattern your heart desires. Sprinkle crumbled gorgonzola on top, then run your fingernails up along the thyme sprigs, popping off the leaves to scatter the thyme over the tart. Return to oven for another 15-20 minutes, until the puff pastry is a rich golden color, and the cheese is melted. Top with toasted pine nuts and drizzled honey, if desired. Slice into desired size slices (I thought 12 looked right) and serve warm or at room temp. Enjoy!