Butter. Put it on everything.
Saturated fat is not only a useful source of long-term energy, but it leads to a feeling of satiety that is otherwise hard to get on a vegetarian diet.
Of the three macronutrients--carbohydrates, proteins, and fats--the fats, especially the saturated fats, have gotten the worst reputation. The book Good Calories, Bad Calories makes a convincing case that the vilification of saturated fats is more political than evidence-based, and it shows that there is significant evidence implicating refined carbohydrates in many chronic diseases attributed to fat consumption.
Even though saturated fats contain twice the calories per gram, carbohydrates--especially sugars--somehow make you more hungry even while you're eating a big meal. This makes it possible to consume a very large amount of carb calories without attaining a feeling of satisfaction. And, if you're eating too many carbs, you're not eating the all-important vegetables and protein. I've found this to be a major problem as a vegetarian. Butter, on the other hand, does lead to a feeling of satiety relatively quickly (try eating a stick of butter if you don't believe me). The result is that it's hard to consume as many calories through butter as through sugar, so you feel more full but you actually have more room for eating nutritious foods like vegetables.
Once you realize that you have nothing to fear, you can put butter on everything.