Sweet Potato and Root Vegetable Gratin with Sweet Potato Sauce

Having already planned the fried chicken night, my goal was to locate a light vegetable side to go with the leftovers the next night. Another piece of my goal was to use some winter roots one more time before the season is gone. Most people are doing their best to rush spring into place, but I wanted to hang on to winter for just a moment longer. In truth, winter is actually already gone here in Austin. It was 88 degrees last Friday, and it’s going to be about 80 each day this week. And, spring doesn’t really happen; it just flits by and waves as it ushers in the ferocious heat of summer. I’m not complaining, really, the summer heat doesn’t bother me too much, but I did want to pretend that winter wasn’t gone just yet.

Needing a light, wintry, vegetable dish led me to Taste Pure and Simple by Michel Nischan. This book is all about applying healthful cooking techniques to pristine ingredients to create dishes that are pure in flavor and not masked by excess seasoning or fat. Fruit and vegetable juices are reduced and made into sauces without added starches or butter, while the main ingredients’ true characteristics are allowed to shine. I’ve had this book for a few years, and the reason I haven’t cooked from it more is that I don’t own a juice extractor. Making this root vegetable gratin with sweet potato sauce depended on locating some sweet potato juice. I wondered if I could find a bottled vegetable juice that would be close or maybe even a squash juice. No such luck. I asked at Whole Foods, and the juice guy, who had never seen sweet potato juice, suggested I sweet talk the folks at the juice and smoothie counter into making some for me. Thank you again to the juice and smoothie counter ladies who so kindly played along and obliged my unique request. They had never juiced sweet potatoes but were willing to give it a try. Two large sweet potatoes produced a large plastic cup full of juice, and all the other ingredients I needed were very easy to find.

The gratin was built with layers of thinly sliced rutabaga, russet potato, sweet potato, and parsnip. The layers were stacked and repeated, and each layer was seasoned with salt and pepper. Minced onion was spread in the middle. This was covered and baked for 50 minutes. At that point, the gratin was removed from the oven, the parchment and foil covering was removed, the top was sprayed with oil, it was sprinkled with chopped parsley, chives, and sage, and it was returned to the oven for another 20 minutes. Meanwhile, the sweet potato juice was poured into a saucepan while leaving the collected starches at the bottom of the cup. It was reduced to one cup and then left to steep with sliced ginger, chopped Thai chiles, and lemon juice. I tasted this as it was stirred and strained the sauce once the ginger and chiles had imparted their flavors.

I wondered if the gratin with no cream or cheese or butter would taste of boringness and earth or if the root vegetables and onion would develop into something fantastic on their own. Develop they did. This was full of bright, vegetable flavor without any heaviness. There is plenty of moisture in the vegetables which prevented the gratin from being dry. Really tasting each vegetable layered upon one another was delightful. The sauce was sweet and spicy and rich but only in flavor. Really experiencing the simplicity of ingredients is a lovely thing, and it greatly reduces the guilt of eating fried food for two meals in a row.