Hi there!

Cornstarch is generally a no-no. If you look around the 'sweet treats' section of the forum, I'm sure you'll find something similar but LC. I seem to remember a lemon curd recipe, and a lemon custard of some kind.

Soy sauce is okay as long as it's sugar and starch free.

Aspartame is probably okay in moderation... I eat a lot of it. Probably too much. It's a YMMV thing. I rarely see products with Splenda. I hope its popularity keeps growing.

HTH!