Migrating from Elixir to Mix (merge & compile multiple sass files)

Hello,

I am migrating my CMS from Laravel 5.1 to 5.5, that means switching from Elixir to Mix too.

In Elixir you could merge & compile multiple sass into 1 target file (app.css) with the following, however this no longer works.

Anyone has a suggestion?

My Elixir script:

mix.sass([
    'guest/app.scss',
    'guest/helpers.scss',
    'guest/pages/landing.scss',
    'guest/partials/cookies_agreement.scss',
    'sweetalert.scss'
], 'public/assets/guest/app.css');