Thickening Eggs with Cornstarch
Let's look at the estimated calories in that recipe:


Eggs: 270
Milk: 12
Cornstarch: 15
Butter: 306


So, given that the single largest source of calories in that recipe is the butter -- more than the eggs! -- if you're looking to reduce calorie count cutting back on the butter to 1 Tbs is the way to go.   Of course, that will affect the flavor as well.  The cornstarch isn't significant in those quantities.

(calorie counts are via Google, but are consistent with what I've seen elsewhere)

My personal perspective is: if you're looking to reduce calories, simply eat less. Compromising flavor in order to save calories is pointless; just make delicious foods in very small quantities.