function booze_entity_info() {
  return array(
    'booze_display' => array(
      'label' => t('Display'),
      'entity class' => 'Drupal\Core\Config\Entity\Display',
      'controller class' => 'Drupal\Core\Config\Entity\ConfigStorageController',
      'config prefix' => 'booze.display',
      'fieldable' => FALSE,
      'entity keys' => array(
        'id' => 'id',
        'label' => 'label', // @todo may not need this if internal-only (?)
        'uuid' => 'uuid',
      ),
    )
  );
}

// and when i call this (when no such config item exists yet):
$display = config('booze.display.foobar');
// i get back an object of type Drupal\Core\Config\Config