i don't think there's currently a way to target one in specific to show up on your mini profile field. mine are showing all of them currently.
<div class="pp-mini-expand">{{#each user.custom_fields}}<div class="pp-mini-field"><strong>{{ this.label }}</strong><span>{{ this.value }}</span></div>{{/each}}</div>
this is basically how mine looks, obviously with the css on my stylesheet but yeah. unfortunately wasn't able to target one profile field in specific unless there's another way to do it.
{{#each user.custom_fields}}
this basically tells the template go through every custom profile field this user has.

{{ this.label }}
displays the name of the custom field.
{{ this.value }}
the content the user entered on the profile.