October 19, 2012
Kale and Spaghetti Squash Gratin and Preventing the Dreaded Curdle
It's fully sweater weather. Which I'm excited about, and not only because its arrival gave me an excuse to gift myself a couple of new cold-weather wardrobe items. I'm also excited because after a summer full of warm weather eating, I'm ready for some food with heft. I'm talking about food that comforts - warms you from the inside out. Just like this gratin.
There can be so much more to gratins than just potatoes. Greens, squash, sweet potatoes, root veggies of all kinds - all can be thrown into a delicious gratin. Layers of veggies and creamy, cheesy sauce - seems fairly straightforward. But it's not. I don't know if I'm the only one, but I think gratins are wolves in sheep's clothing.
The most awkward part about making gratins, my number one fear, is the risk of the curdle. There's nothing worse than putting time and energy into making a gratin, slicing potatoes with precision, creating neat layer after layer - only to pull it from the oven, dig in and find your perfect potatoes swimming in curds and whey. Unless your dinner guest is Little Miss Muffet, I'll bet a split, curdled sauce is not exactly what you had in mind.
There are a lot of reasons why gratins curdle. The two biggest offenders are acid splitting the sauce and baking the gratin in an oven that is too hot.
Because the cream sauce in a gratin is often comprised of whole milk, cream or half and half, the sauce runs a pretty high risk of splitting when anything with a smidgeon of acid in it gets involved. Acid is in most of the foods that you might add to that gratin - leeks, onions, garlic, herbs. In order to considerably lower this risk, take the time to build a stable cream sauce before putting the gratin together. This means making a bechamel sauce as your foundation instead of just pouring milk or cream over the sliced potatoes in the dish and adding cheese and breadcrumbs on top. So, start with a roux, I made mine with half butter and half oil, and then slowly whisk in the warm liquid and a bit of cheese. It's a bit more of a hassle, but worth it in the end.
Now that you've gone to the trouble of making the sauce, be sure to give it a fair chance by letting that gratin cook on a lower temperature than you would normally - try around 325ºF - placing it uncovered under the broiler for the last few minutes to brown the top. Allowing the cream sauce to violently bubble and boil for a long time in the oven will almost definitely split it.
I guess this isn't technically a 'gratin' because I omitted breadcrumbs from the top. I didn't have any on hand, nor did I have the bread to make some - but you could definitely add a layer on top, which you would do just before baking.
Fills one 8'' round baking dish
What you'll need:
1 small spaghetti squash, one that weighs ~2 lbs
2 Tbsp butter
2 Tbsp olive oil
1 large onion, cut into 1/2 inch dice
4 cups baby kale (or 1 large bunch kale of your choice)
2 Tbsp flour
1 1/4 cups half and half, maybe a bit more
1/2 cup Parmigiano-Reggiano, freshly grated
Preheat the oven to 375ºF
Cut the spaghetti squash in half, place each half, cut side down, on a parchment lined baking tray. Bake for 30 minutes.
Remove from oven and allow to cool until you can handle it.
Use a spoon to remove the seeds from the squash. Then, using a fork, scrape back and forth, creating long strands of 'spaghetti.'
Once each half has been scraped clean, discard the skins and set the bowl of spaghetti squash aside.
Gently warm the half and half in a small pot on a back burner, keeping an eye on it to be sure it doesn't boil over.
In a wide pan, sauté the diced onions in the butter and oil over medium-low heat, until they begin to brown - around 15 minutes.
Add the kale to the onions and season with salt, pepper and cayenne. Stir to incorporate.
Once the kale has wilted, sprinkle with the flour and stir well - until the flour is transluscent and sticks to the veggies.
Using a whisk, slowly incorporate the warm half and half, until it thickens to a sauce.
Bring to a simmer, stir and if the sauce is gloppy and too thick, add a bit more half and half until it is thinned - it should coat the back of a spoon.
Add half of the cheese, stir to melt it and turn off the heat.
Add the squash to this mixture. Stir well to coat and transfer the entire mixture to a baking dish.
Top with the remaining cheese and place under the broiler for 8-10 minutes, until the cheese is golden brown.