Query for specific custom field

Question

Data associated to a user can be saved in user meta. Save the recipe post IDs in an array for the user.

$my_favs = array( 42, 23, 99 );
update_user_meta( get_current_user_id(), 'user_favs', $my_favs );

Then to query all recipe posts with those IDs, pass the array as the post__in argument to WP_Query:

$my_favs = get_user_meta( get_current_user_id(), 'user_favs', true );
$args = array(
    'post_type' => 'recipe',
    'post__in'  => $my_favs,
);
$recipes = new WP_Query( $args );