So in response to @papa-pepper's steemgig here I've created AskSteem User Explorer, a tool that allows searching by user and tag easier than the standard AskSteem interface.

How to use it:

First, you need to visit asksteem.com/userexplorer

Then enter your username into the box marked username and enter a tag into the box marked tag. Hit return on your keyboard and you will be taken to a page with a reverse chronological list of all posts that user has created in that tag.

Happy searching!