Siri shortcuts voice input
Yay my first Shortcuts question!

Use the Dictate Text action.  



This action will convert words you speak into to text and pass that text to the next action.

Currently, there is a bit of down side: You will not be able tell Siri in one sentence "Tell [Shortcut Trigger], Apples are cool" Instead you need to do it in two parts "[Shortcut Trigger]" wait... "Apples are cool".

Warning: Make sure to pick a language or it will silently fail.