You could use red onion or shallots in lieu of the spring onions, and substitute for or skip the peas - but if you find pea tendrils, you shouldn't have trouble finding peas!
Bring a pot of salted water to the boil and add your pasta. About 2 minutes before it's done, throw the peas in with it to blanch them.
In a large sauté pan, lightly sauté the garlic in olive oil.
After a minute, and without letting the garlic start to toast, throw in the spring onions.
After a minute, pour in about half a cup of stock. If you prefer, use some reserved pasta water instead.
Add salt and a few grinds of pepper, and turn up the heat to bring it to a boil.
Meanwhile, after the peas have been in with the pasta for 30 seconds or so (which should also be a minute or two before the pasta is finished cooking to your liking), drain the pasta and peas.
Throw the pea tendrils into the saute pan with the other ingredients and toss to coat.
Throw the pasta and peas into the sauté pan and cook in the remaining liquid until it's mostly absorbed and the pasta is cooked to your liking. I like mine al dente.
After turning off the flame, pour a little finishing oil in and adjust the seasoning to taste. You could try substituting a little butter if you wanted to make it richer.
It came out pretty well - a nice showcase for the delicate flavor of the pea tendrils. If I'd had any good parmesan cheese on hand, I would have grated a little on.
I was pretty happy with the way this came out, but I have no idea if this approach was optimal or not. I'd appreciate if people left comments or suggestions on how to improve.