Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.7)
// Compass (v1.0.1)
// ----

$map: (
  main-key-1: (
    (key-1: value-1, key-2: value-2),
    (key-1: value-3, key-2: value-4)
  ),
  main-key-2: (
    (key-1: value-5, key-2: value-6),
    (key-1: value-7, key-2: value-8)
  )
);

@mixin mixin() {
  @each $main-key, $sub-map in $map {
    @each $key, $val in $sub-map {
      .element-#{$main-key} {
        content: 'key: ' + $key;
        content: 'val: ' + $val;
      }
    }
  }
}

@include mixin();

SassMeister-output.css

.element-main-key-1 {
  content: "key: key-1 value-1";
  content: "val: key-2 value-2";
}

.element-main-key-1 {
  content: "key: key-1 value-3";
  content: "val: key-2 value-4";
}

.element-main-key-2 {
  content: "key: key-1 value-5";
  content: "val: key-2 value-6";
}

.element-main-key-2 {
  content: "key: key-1 value-7";
  content: "val: key-2 value-8";
}