winter/modules/backend/routes.php

<?php

/**
 * Register Backend routes before all user routes.
 */
App::before(function ($request) {
    /*
     * Other pages
     */
    Route::group(['prefix' => Config::get('cms.backendUri', 'backend')], function () {
        Route::any('{slug}', 'Backend\Classes\BackendController@run')->where('slug', '(.*)?');
    });

    /*
     * Entry point
     */
    Route::any(Config::get('cms.backendUri', 'backend'), 'Backend\Classes\BackendController@run');
});