Thursday, July 29, 2010

0 Recipe #152: Potatoes & Butternut Squash Au Gratin

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What can I say, I've been in a cheese mood lately. :) This type of hearty, piping hot dish is probably best suited for fall & winter, but since the other, remaining half of a butternut squash had been staring back at me in my fridge for about a week now already, sometimes a chef's gotta do what a chef's gotta do to avoid kitchen waste. :)

And thankfully, this recipe popped out of my head just in time, almost as if by magic. Necessity is indeed the "mother of invention." :)

While this dish might be suited to a colder clime &/or season, its ingredients are seasonless: Even though butternut squash is classified as a "winter squash," thankfully, it's available all year round, with its peak season being fall through winter.

This recipe has been tweaked a bit from its original concept: I originally tried making this dish with celeriac, in addition to the other ingredients, but after tasting it, decided it would be better without it. Celeriac can often be bitter, even after it's been cooked, & it takes an awful lot of fussing & messing around with it to lessen its bitter taste. And honestly, if it requires that much extra doctoring to make it work in a casserole, then that's probably a sign that it shouldn't probably be in there in the first place. ;) Celeriac tastes great when it's been marinated, but of course a gratin is not something that should be marinated. :) Guess I just wasn't in the mood to soak the celeriac in lemon juice for 5 years before baking it. ;) The addition of celeriac was a nice idea in theory, but the texture & flavor of the squash & the potatoes are a perfect complement to each other (& to the other existing ingredients in this dish) in & of themselves. I've learned the hard way that it pays to follow your gut instincts in the kitchen. When you inner chef says it's time to stop adding ingredients, it's best to listen. :)

Potatoes and butternut squash, ahhhhhhh, what a tasty combination. And, on that note, I give you....

Potatoes & Butternut Squash Au Gratin

Gratin Bake Ingredients:
10-12 c. lightly salted water
4 1/2 c. butternut squash, peeled, with seeds & strings scooped out of inner cavity, & thinly sliced into 1/8" thick rounds (about 1 medium-sized squash)
4 1/2 c. red-skinned potatoes, peeled & thinkly sliced into 1/8" thick rounds (about 2-3 medium-sized potatoes)
2 Tbsp. fresh thyme leaves
1/4 c. Asiago (or Parmesan) cheese, freshly shredded
2 Tbsp. plain bread crumbs (panko or homemade)

Sauce Ingredients, Part 1:
1 Tbsp. extra virgin olive oil
1 c. whole leek, sliced into 1/4" thick rounds (about 1 small leek)
1/2 c. celery (about 1 medium-sized stalk)
3 Tbsp. shallot, finely minced (about 2 large shallots)
1 large bay leaf
1 Tbsp. fresh sage, julienned
1/2 c. (dry) sherry
1 1/2 c. light plain soy milk

Sauce Ingredients, Part 2:
1/2 Tbsp. unsalted butter
1/2 Tbsp. unbleached, all-purpose flour
1/2 c. skim milk
2 c. reduced-fat Cheddar cheese, shredded
1 c. part-skim, nonfat ricotta cheese
1 tsp. kosher salt
1 tsp. ground black pepper
1 tsp. dried marjoram leaves
1/2 tsp. dried, ground (yellow) mustard

Directions: With a spray bottle or Misto oil diffuser, spray a 9 x 13" rectangular Pyrex glass casserole dish with olive oil. (Or just use a pastry brush if you prefer.) Set aside.

Next, bring 10-12 c. of lightly salted water to a boil in a large stock pot. Then add sliced potatoes & butternut squash & boil (on high heat) for about 15 minutes, or until almost tender. IMPORTANT: When ready, the vegetables should still be somewhat firm & slightly undercooked; since you'll be baking them later, you don't want them to be completely cooked all the way through at this point.

While vegetables are boiling, sauté leek & celery in olive oil on low heat in a large, deep, nonstick sauté pan until almost tender, about 3 minutes. Then add shallots & bay leaf & cook for another 2 minutes. Do not allow ingredients to brown or burn. Add sage & then deglaze with sherry, continuing to cook for another 5-7 minutes or so, or until liquid has been reduced to only a thin layer on the bottom of the pan. Remove from heat & let cool. Remove & discard bay leaf & then transfer mixture to a blender. Add soy milk, & pulse until smooth. Set aside.

Next, make the roux & cheese sauce: In a medium-sized nonstick sauce pot, melt butter on low heat & then immediately whisk in flour, followed in rapid succession by the milk, cheddar & ricotta cheeses, salt, pepper, marjoram, & ground mustard. Transfer leek-shallot-celery mixture from blender to the sauce pot & continue to stir until well-combined. Remove from heat & set aside.

When vegetables have finished cooking, drain in a colander, run under cold tap water to cool, & then drain once more, gently shaking off excess water. When vegetables have adequately cooled, start assembling gratin/casserole, taking particular care in handling the squash, which can be brittle after cooked: Layer slices of  potatoes & squash in an overlapping (i.e., "scalloped") fashion. (I like to make striped rows of each vegetable type, but you can do whatever patterns you like.) After each full vegetable layer has been completed, pour a thin layer of the cheese-leek mixture over each layer of sliced vegetables, followed by an evenly distributed sprinkling of Asiago (or Parmesan) & thyme leaves. After the final layer has been completed & topped with sauce, Asiago, & thyme, sprinkle a fine layer of bread crumbs across the top face of the casserole. Cover casserole dish with aluminium foil (shiny side facing downward), & bake for about 30-35 minutes on 375°F. From a safe distance, open oven, slide out rack holding casserole dish (using silicone mitts or grippers), & carefully peel back foil using heat-proof tongs, watching for escaping steam. Slide rack back into the oven, and cook casserole, uncovered, for 25-30 more minutes, or until vegetables have become tender & the casserole's top has turned golden-brown. (It should also be bubbly. Do not overcook, or casserole will be dry & brittle.) About 10-15 minutes into cooking, test casserole with a knife or fork; if the tip of the knife/fork goes in with little resistance, it's done. Let cool slightly before serving.

Yield: Makes approximately 12 square portions, about 3 square inches per person.

Chef's Notes: Potatoes discolor/oxidize soon after their flesh is exposed to air. Therefore, it's important that the slicing & boiling steps be particularly well-coordinated with one another. If you chop all the vegetables at the same time you're waiting for the water to boil, everything should be timed just perfectly. I'd also recommend that you peel & slice the vegetables according to their oxidation rates: In other words,  prepare/slice the butternut squash first, followed by the potatoes. (Whatever oxidizes first is what's going to be peeled & chopped last.) If necessary, you can soak the potatoes in acidulated water (i.e., water with a few tablespoons of fresh lemon juice or distilled white vinegar).

This dish would also taste good with mushrooms &/or cauliflower.

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