Cypress.io How to handle async code

I'm in the middle of process of moving our old capybara tests to cypress.io as our application is going SPA way.

In our case we have over 2000 tests covering a lot of features. So common pattern to test feature is to have an user with created and published offer.

On the beginning I wrote case where cypress were going trough page and clicking everything. It worked but I saw that offer create + publish took almost 1,5 minute to finish. And sometimes we need multiple offers. So we have a test which takes 5 minutes and we have 1999 left to rewrite.

We came up with REST API to create offer and user, basically shortcut for test env preparation.

I came to the point where everything is working using async/await. So here's the thing. If I want to use normal async JS code with cypress I get Error: Cypress detected that you returned a promise from a command while also invoking one or more cy commands in that promise.

Here's how it looks like:

    const faker = require('faker')
    import User from '../../support/User';

    describe('Toggle button for description offer', () => {
      const user = new User({
        first_name: faker.name.firstName(),
        last_name: faker.name.firstName(),
        email: `QA_${faker.internet.email()}`,
        password: 'xxx'
      })
      let offer = null

      before(async () => {
        await user.createOnServer()
        offer = await user.createOffer()
        await offer.publish()
      })

      beforeEach(() => {
        user.login()
        cy.visit(`/offers/${offer.details.id}`)
        cy.get('.offer-description__content button').as('showMoreButton')
      })

      it('XXX', function () {
        ...some test
      })
    })

This snippet works as expected. Firstly it fires before and creates whole env then when it's done it goes further to beforeEach and starts testing.

Now I would like to merge before and beforeEach like

  before(async () => {
    await user.createOnServer()
    offer = await user.createOffer()
    await offer.publish()
    user.login()
    cy.visit(`/offers/${offer.details.id}`)
    cy.get('.offer-description__content button').as('showMoreButton')
  })

Which will fail because of async keyword. Now the question is: how to rewrite it to use async/await and cypress commands together? I tried to rewrite it with normal Promise but It won't work too ...

Any help appreciated.