Shrimp Fettuccine Alfredo

In large pot of boiling water, cook fettucini until it's al dente, about 10 minutes.
Drain well, and return to pot.
Mean while, whisk cornstarch into milk and set aside.
On medium heat, heat oil and butter in a large frying pan.
Cook garlic for about 5 minutes or until soft but not browned.
Mash soft garlic with the back of a fork.
Add peeled shrimp and onions.
Cook just until shrimp turns pink, about 1 1/2 minutes (shrimp will continue to cook as you add the rest of the ingredients).
Briefly stir milk mixture and pour into frying pan.
Cook, stirring constantly, until slightly thickened, about 2 minutes.
Pour mixture over fettucini.
Sprinkle with Parmesan cheese.
Add salt and pepper to taste.
Stir to combine.