Day 25: Warm Sweet Onion Tart

I know, I know, and you're right -- I did say in yesterday's post that I'd be making pizza tonight, but later that night I received an email from my friend Jennevieve inviting us over to a last minute dinner party.  There is no way I'm missing dinner at Jennevieve's, let me tell you!  She's a fabulous cook and a great hostess.

Now you're probably thinking, here she goes skipping another night of cooking, right?  WRONG!!  I'll be bringing an appetizer from A Great American Cook, Warm Sweet Onion Tart.

Starting to cook onions

The recipe calls for puff pastry as the crust.  I didn't have any on hand (have never used it) so off to the store I went for a tart pan, and some puff pastry.  I followed the recipe religiously with disastrous results -- at least as far as the puff pastry was concerned.  It pulled away from the edges, and puffed (I suppose I should have blind baked it)!  I didn't have enough time to defrost the other sheet of puff pastry, so I pulled out my handy-dandy Pillsbury pie dough.  Now one day I will learn how to make pie dough, but until then I will use this dough, it's my favorite.  I carefully pressed the dough into the pan, and popped it in the fridge to chill a bit.  This time I lined it with foil, filled with my bean "weights" before I baked it.

After cooking 30 minutes on low.

Now the onions were only supposed to take 30 minutes, but it was probably closer to an hour (maybe I had the flame on too low).  Luckily I started cooking early so I had some wiggle room.

Warm Sweet Onion Tart
A Great American Cook
Yield:  6 servings

2 large sweet onions, such as Vidalia
4 tbsp (1/2 stick) unsalted butter
1/2 cup balsamic vinegar
Kosher salt and freshly ground black pepper
1/2 pound puff pastry, preferably an all-butter brand such as Dufour (or 1 sheet pastry from a 17 1/4 ounce package)
2 large eggs
1/2 cup heavy cream
1 few thyme blossoms or 1 tsp fresh thyme leaves

     Slice the onions crosswise as thin as possible.  Place a large skillet over very low heat.  Add the butter and when it melts, stir in the onions.  Cook, stirring occasionally, for 30 minutes, or until the onions are very soft and deep golden brown.
     Add the vinegar to the onions and cook until it is has reduced and slightly thickened, 5 to 10 minutes.  Remove from the heat and let cool, then season with salt and pepper.
     Heat the oven to 400 degrees.
     On a lightly floured surface, roll out the puff pastry 1/4 inch thick.  Using a pot lid or a plate as a guide, cut the pasty into a 10 inch round.  Fit the pastry onto an 8 inch tart pan with a removable bottom.  Trim the edges of the pastry if necessary and prick it all over with a fork.  Bake for 15 to 20 minutes, or until golden brown on the bottom.  (Don't be afraid that the tart shell will burn later when it is baked again -- the filling will prevent that from happening.)  Take the tart shell out of the oven and let cool on a rack for 10 minutes.
     Whisk the eggs lightly in a medium bowl.  Add the cream and thyme and blend well, then season with salt and pepper.  Spread the onions evenly in the tart shell.  Pour the egg mixture over the onions and stir gently with a fork so the custard mixture spreads evenly in the tart shell.
     Bake the tart for 25 minutes, or until just set.  Remove and let cook on a rack.  Serve warm or at room temperature, cut into wedges.

Update:  I had baked the tart for 20 minutes since the instructions said 25 minutes or until eggs set (the eggs seemed set).  It wasn't cooked all the way through so Jennevieve had to pop it into her oven for another 5 to 10 minutes.  That little snaffu aside everyone seemed to loved the tart.