French Onion Tart

It's almost Mothers' Day, but don't panic if you don't have a gift (yet). I can assure you that impressing your mom with a lovely meal will mean a lot to her, so I have another recipe to contribute to your fancy menu (it also goes well with scallops): French onion tart. It's like French onion soup but with bacon and a buttery crust, so basically it's a million times better.

I start with a simple savory pie crust, which is just flour, butter, and a smidgen of salt and sugar. Everything is minimally pulsed together in a food processor until just combined, and the dough is kept cold right up until baking. Having small bits of cold butter makes the pie crust flaky since they melt to create steam and therefore flaky bits. For this recipe, I blind bake the crust before baking the whole tart so that it doesn't absorb too much moisture from the filling and become soggy. I chose a rectangular tart pan to maximize the number of end pieces, but any shape or size will do, though you may have to adjust baking times and serving sizes. Immediately after it comes out of the oven, I sprinkle it with the gruyere, which melts and forms a barrier between the crust and the filling to prevent moisture migration and sogginess. I prefer gruyere because that's what is traditionally used in French onion soup, but any mild melting cheese will work.

The filling starts with bacon, and lots of it. I always make even more so I have some to snack on while cooking the rest of the tart. However much you decide to make, cook it all in a big skillet until it's crispy and most of the fat is rendered off. Remove it with a slotted spoon so you save all the drippings (this is very important) and chop into small pieces when cool.

The reason it's so important to save the bacon fat is so you can cook the onions in it. This eliminates waste, saves you from buying/using other ingredients, and, most importantly, adds even more bacon flavor to the tart. I suppose you could saute the onions for only a few minutes until tender and translucent, but I let mine fully caramelize like French onion soup onions would be. One of my cooking secrets is adding a little bit of baking soda to caramelized onions towards the end; as I've said in earlier recipes, it makes the system more acidic, promotes Maillard browning, and makes the onions much darker. It's a great alternative to having only semi-caramelized onions. I recently tasted a product that caramelizes onions almost instantly, but unfortunately that's a top-secret recipe only available to restaurants and processed food producers.

Most of the work is done once you've finished the crust, bacon and onions. The only other ingredients in the tart are eggs and sour cream, which I whisk together before adding the onions. That mixture is poured into the crust, sprinkled with the bacon and remaining cheese, and baked until golden brown and set. You may have some extra filling, but it can be refrigerated for a day or two until you have time to make more crust to bake it in. You could also go the crustless quiche route and bake it in greased mini muffin tins for a quick snack. I still prefer the big tarts since they just look so elegant and pretty, perfect for Mothers' Day!

1 Recipe Savory Pie Crust Dough (Below)
3/4 Cup Shredded Gruyere
1/4 lb Bacon, Diced
2 lbs Onions, Sliced Thinly
Pinch Baking Soda
2 Eggs
2/3 Cup Sour Cream

Blind bake the crust in a tart pan. Sprinkle immediately with 1/2 cup cheese. Leave oven at 350°F.

Cook the bacon in a skillet until crispy. Drain, reserving the fat, and chop.

Add the onions to the skillet with the bacon fat and cook over low heat for 30-40 minutes, stirring occasionally, until caramelized, adding the baking soda halfway through. Season with salt and pepper.

Combine the eggs and sour cream. Stir in the onions and season with salt and pepper.

Spread the filling into the crust and top with the bacon and remaining cheese. Bake for 30-40 minutes or until golden.

Crust:
1 1/4 Cups Flour
1 1/2 tsp Sugar
1/2 tsp Salt
1 Stick Butter, Chilled & Cubed

Pulse the flour, sugar, and salt in the bowl of a food processor to combine. Add the butter and pulse until small lumps remain, then drizzle in cold water until it clumps together.

Recipe Adapted from Smitten Kitchen and Gourmantine's Blog