Laravel 5.4.22 PHP - Trying to just hook up this route to simply post the data to the page

So Im currently building a simple email registry, and my issue is that I am recieving a MethodNotAllowedHttpException for posting.

Here is my Register.php controller

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class Register extends Controller
{
    public function validateCredentials()
    {
      $email = Input::post('emailInput');
      return "Email: " . $email;
  }
}

Im simply just running these routes currently

Route::get('/index', function(){
    return view('index');
});
Route::post('/index', 'Register@validateCredentials');

Im assuming the bulk of my issue is located inside of my form itself:

<form method="post">
    @CSRF
    <input type="email"
           placeholder="Your email"
           name="emailInput"
           class="ct"/>
    <input type="submit"
           value="Sign Up"
           name="submitInput"
           class="bbg vtm"/>
</form>

via Chebli Mohamed