The phrase "a most efficient" is correct and usable in written English.
It can be used to emphasize the high degree of efficiency of something, often in a formal or literary context.
Example: "The new software proved to be a most efficient solution to our data management issues."
Alternatives: "an extremely efficient" or "a highly efficient".
The results of our evaluation show that recommender algorithms, such as CF-shrinkage, CF-significance weighting, and BRISMF, when applied in the context of product-line configuration can efficiently support decision makers in a most efficient selection of features.
Numerical weather forecast is a most efficient means to reduce the effects of unexpected weather events.
Alternatively, a most efficient control strategy based on shape optimization has been thoroughly investigated.
Fire is a most efficient destroyer; when the flame no longer exists there is virtually nothing left of the objects.
Sophisticated parallel computing system necessitates solving the bus contention in a most efficient manner with high computation rate.
The best results have been obtained by applying an empirical method based on the optimization of all the empirical constants through a most efficient mathematical tool.
These tasks determine the requirement specifications for a direct, most efficient (optimal) engineering design of the IMS main components.
So I decided to calculate the travel time that it would take to work your way around the world, in an order most efficient for accomplishing each of the BuzzFeed tasks.
As a result, the most efficient combination for a given resource constraint is identified.
The name says it all for "The Straits," which surely deserves an award for most efficient use of a title by a contemporary British playwright.
FBA A, which is the most efficient in glycolysis, is the major form present in muscle.
