On the twenty twelve theme, that doesn't produce the correct result as it places a <title> tag at the very beginning of the (Woocommerce) base shop page ... before all other HTML.
That's incorrect; you end up with 2 <title> tags on your page, as well as invalid HTML.
Instead, if you have Yoast's WordPress SEO plugin installed ... do this:
- Visit http://yourdomain.com/wp-admin/admin.php?page=wpseo_titles#top#post_types
- At bottom of that page in the "Custom Post Type Archives" section, enter your desired title in the "Title" field.
- Example: Vanilla Ice Cream
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DONE