vegan fettuccine alfredo

This was a new one for me- and another one that tasted better as a leftover since the alfredo like sauce got harder.
Ingredients:
fettuccine
mushrooms
asparagus
3 TBsp garlic
1/2 cup soy milk
1/4 cup nutritional yeast
1/4 cup vegan margarine

I cooked the fettuccine like any pasta while making the sauce. And the asparagus and mushrooms- I just had some in the fridge so decided to use them in the dish- I boiled them separately while working on the sauce.
For the sauce:
Saute the garlic and margarine until garlic is browned.
Add the yeast and whisk until blended in, cooking at medium-high.
After a couple minutes add the soymilk and whisk in. Turn down to simmer and continue to whisk until becomes thick...(This was the tough part for me, it didn't really thicken like most of the creamy recipes I make).
Then toss with the fettuccine and asparagus and mushrooms. It was tasty, but here you can tell it was a little soupy with regards to the sauce. However, I put a lot in containers as leftovers, and those congealed so that when it was reheated in the microwave it was the perfect, expected alfredo sauce consistency!