models.coffee

Recipe = DS.Model.extend
  title: DS.attr('string')
  steps: DS.hasMany('step', {async: true})

Step = DS.Model.extend
  substeps: DS.hasMany('substep', {async: true})
  
Substep = DS.Model.extend()

recipe.hbs

<h1>{{title}}</h1>
<ul>
{{#each step in steps}}
  <li>{{id}}</li>
  <ul>
  {{#each substep in substeps}}
    <li>{{id}}</li>
  {{/each}}
  </ul>
{{/each}}
</ul>

recipe.json

{
  "steps": [
    {
      "id": 1,
      "substep_ids": [
        1,
        2
      ]
    }
  ],
  "substeps": [
    {
      "id": 1
    },
    {
      "id": 2
    }
  ],
  "recipes": [
    {
      "id": 1,
      "title": "Scrambled Eggs",
      "step_ids": [
        1
      ]
    }
  ]
}

recipes.json

{
  "recipes": [
    {
      "id":1,
      "title":"Scrambled Eggs"
    }
  ]
}