It's not any one food, it's your entire diet and lifestyle.
Rely on unsaturated and polyunsaturated fats high in omega 3s for the majority of your staple calories, as opposed to carbohydrates. Make the carbs you do eat unrefined whole grains, so that you absorb them slowly. Plenty of complete protein, overwhelmingly from plant sources, always eaten with ample good fats. A good range of phytonutrients from 4-6 different quality raw (or properly dried, home canned, or pickled) fruits & veggies. Fiber is your friend -- eat the whole fruit / veggie, don't juice. Consider supplementing a time-release B complex vitamin. Chew your food thoroughly, eat slowly, drink plenty of ice-cold water (cold is a metabolic stimulus in the short term), and eat many small meals. Consider replacing anything in your diet that comes from a factory with something that doesn't. Eat out much, much less. Drink only water, black coffee, plain tea, or homemade infusions. (Quality coffee and green tea, prepared properly, should have a naturally sweet edge and neither should need anything to enhance or apologize for their natural flavors.) Cheat and indulge in your favorite junk food semi-regularly. I said indulge, not binge. Practice good sleep hygiene: go to sleep as close to the same time every day as possible, in a very dark room, and don't eat <2h before bed. Learn to notice and appreciate the subtly stimulating effect of short semi-frequent fasts, and stop being afraid of going 12~18h 1-2x/wk without taking in anything besides some basic liquids -- our ancestors did it all the time out of necessity, and our bodies are built to handle it, probably better than they're built to handle a constant onslaught of feasting and sitting. Acclimate yourself to the cold in winter by being more physically fit and moving around more, and gradually wear less and lower your thermostat. But be warm to sleep, at all costs.
It might be counterintuitive to think that by relying on more fats for your energy supply, you'll burn off fat stores. But it actually does make sense when you consider that you're upregulating the metabolic pathways that use fats as fuel; when you're between meals and your blood glucose is lagging, your body will dig into your fat stores even more than if you're used to running on mainly carbs.