Caramelized Onion & Cauliflower Tart

I haven't posted a recipe in quite some time. While I'd like to tell you its because I've been traveling the globe exploring far off places, I've really just been busy with work and family. I was fortunate enough to get to visit San Francisco at the end of November and found some real restaurant gems that I could talk about for hours - - Scoma's, Wayfare Tavern, Waterbar - - just to name a few! All that and my husband got to see Alcatraz for the first time and visit the Mikkeller and 21st Amendment breweries. Come to think of if, maybe I should do an entire blog post dedicated to that trip if people would be interested. It was quite the foodie adventure!

Amazingly, the end of the year is fast approaching so in the midst of the busy holiday season I wanted to share one of my all time favorite dishes that is perfect for Christmas and New Year's guests. Delicious eaten warm out of the oven or at room temperature this tart is absolutely decadent. It's also a show stopper. It is one of the dishes I get asked about most frequently from people who I've made it for, and it has garnered favor with everyone from young children to my parent's retirement community of friends. How's that for range?  If you're looking for something special to make this year to really wow your family and friends, this would certainly fit the bill.

You want to see those roasted brown nuggets of goodness! 

To get started, position the rack in the center of the oven and preheat to 425°F. Scatter the cauliflower onto a rimmed sheet pan and toss with several tablespoons of olive oil, salt and pepper. Roast for 15 minutes. Turn the cauliflower over and continue roasting until it is brown and tender. This will depend on your oven and the size you chopped the flowerets so just keep an eye on it. Once its done cooking, remove it from the oven. The original recipe calls for a drizzle of truffle oil and/or truffle salt when you remove it from the oven, but if you don't want to splurge to buy that or don't care for the flavor you can certainly leave it off.  After you take out the cauliflower, reduce the temperature to 350°F.

The blind baked crust is cooling and ready for
the delicious filling.

A close up for how you should slice the
onion.  Its a bit different than the norm.

While the cauliflower is getting all roasted and delicious, I encourage you to try your hand at making the tart crust.  If you don't have time or the inclination, then by all means use a store bought crust. No one will care and it will still be delicious. If you are using a store bought crust, press it onto the bottom and up the sides of a 9-inch tart pan.  If you have one with a removable bottom, that would work nicely for presenting the tart outside of the pan. Gently line the crust with foil, fill with pie weights (or dried beans) and bake for 20 minutes. Remove the foil and weights and bake again until the crust is golden, about 5 more minutes. If it puffs up a little bit that is ok, just press it back down gently when you remove it from the oven. All that fuss is called blind baking. It's going to ensure the crust doesn't get soggy when you add the wet filling later on. (If you make the crust recipe listed below, you do NOT need to blind bake it.) Once blind baked, allow the crust to cool.

You will start to see the onion
brown slowly.  Be patient!

To caramelize the onions, heat a couple of tablespoons of olive oil in a large skillet over medium-low heat. I love to use my stainless steel skillet when making these onions. You don't need a non-stick surface and it helps with the color and browning you are looking for. But any large heavy skillet will work. Add the thinly sliced onion, season with salt and pepper and then cook until it becomes a dark golden brown color. You will want to stir it occasionally to keep it from getting too dark in places. I find this process takes anywhere from 30 - 40 minutes depending on the size of the onion I'm using and the heat level of the pan. Once cooked, allow them to cool slightly.

The finished caramelized onion
goodness.  Mmmmm!

Spread or brush the bottom and sides of the crust evenly with the mustard. Sprinkle the cooked onions over the crust and then place the cooked cauliflower on top of the onion. When you bake the tart, be sure to set it on top of a sheet pan so if it leaks you don't have a mess on your hands. Whisk the eggs, mascarpone, cream, and pepper in a medium bowl. Stir in the Gruyère. Once well combined, you are going to pour this mixture over the fillings in the tart pan and sprinkle liberally with the Parmesan. Pour slowly so the mixture can work its way into the nooks and crannies of all of the filling. Don't overfill the shell.  If you have too much of the custard mixture don't force it. Bake until it is golden on top and the center is completely set, 35-45 minutes. 

You can serve it after it has cooled slightly all the way to room temperature.  Refrigerate leftovers covered tightly with plastic wrap or in tupperware.  If you decide to give it a try, let me know what you (and your guests) think.  Or maybe wait and make it after the mad rush of the holidays are over when you can enjoy it solo as a special treat.  Either way, you can't go wrong.

Caramelized Onion & Cauliflower Tart
Adapted from Smitten Kitchen and Bon Appetite, 2007

1 small head of cauliflower, cut into small flowerets
Olive oil
1 large onion, halved lengthwise and very thinly sliced
2 Tbsp Dijon mustard
2 large eggs
1 (8- ounce) container mascarpone cheese
1/2 cup whipping cream
1/4 teaspoon black pepper
1 cup grated Gruyère cheese
1/3 cup Parmesan cheese

Truffle oil or truffle salt (optional)
1 refrigerated pie crust or a homemade tart shell (recipe below)

Savory Tart Shell - recipe from Smitten Kitchen

1 1/4 cups flour
1 tablespoon plus 2 teaspoons cornstarch
1/4 teaspoon salt
6 tablespoons butter, cut into 1 inch pieces
1 egg

In a large bowl, combine flour, cornstarch and salt. Cut the butter in with a pastry cutter, fork or two knives until it is in very tiny pieces. Add the egg and mix with a fork until a dough forms. I usually find that I have to dump it out onto the counter and give it some old fashioned kneading to get it to come together properly.  

Just when you think its a failure and you should have just bought a store bought crust, it takes the heat from your hands and becomes the savory tart dough you've been dreaming of.  Once combined, on a lightly floured surface, roll the dough out to a 12-inch circle. Place the dough in a 9-inch pie plate or tart pan and press lightly to remove any air bubbles or gaps. If it breaks or tears, just piece it back together and mend the flaws.  No one will see them in the end. Clean up the edges, and refrigerate for 30 minutes. Proceed with a filling of your choice, no blind baking required.