Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.4)
// Compass (v1.0.0.alpha.18)
// ----

//
// map-fetch($map, $keys)
//
// An easy way to fetch a deep value in a multi-level map. Works much like
// map-get() except that you pass multiple keys as the second parameter to
// go down multiple levels in the nested map.
@function map-fetch($map, $keys) {
  @each $key in $keys {
    $map: map-get($map, $key);
  }
  @return $map;
}

$config: (
  themes: (
    mist: (
      header: #dcfac0,
      content: #00968b,
      footer: #85c79c
    ),
    spring: (
      header: #f4fac7,
      content: #c2454e,
      footer: #ffb158
    )
  )
);

@each $theme in map-keys(map-get($config, themes)) {

  .#{$theme} {
    .header  { background-color: map-fetch($config, themes $theme header  ); }
    .content { background-color: map-fetch($config, themes $theme content ); }
    .footer  { background-color: map-fetch($config, themes $theme footer  ); }
  }

}

SassMeister-output.css

.mist .header {
  background-color: #dcfac0;
}
.mist .content {
  background-color: #00968b;
}
.mist .footer {
  background-color: #85c79c;
}

.spring .header {
  background-color: #f4fac7;
}
.spring .content {
  background-color: #c2454e;
}
.spring .footer {
  background-color: #ffb158;
}

My map get works nearly the same, but with ($keys...) as the second argument so it's all comma-separated, rather than spaced (sass-list-maps)

Yeah, it's basically the same thing.