A stub that returns a stub

Let's say you have code that returns an object containing pre-programmed functions, which you use like this:

someFunction(/* pass in data */)
  .post(/* some data */)  //Returned post function is pre-programmed to send a POST request to the right URL
  .then(function() {
    //do something
  });

How can I unit test this using sinon.js?

To direct what a function returns, you need to use a stub:

var mockService = sinon.stub();
mockService.returns(/* some return value */);

But let's say I want to verify that someFunction was called with the right arguments, in addition to verifying that the returned post function was called with the right arguments. I would need a stub to return a stub:

mockService.returns({
  post: sinon.stub()
});

How can I access mockService.post to verify that the right arguments were passed, in this case?

Bonus Question: What's the name of this design pattern (returning a function with pre-programmed behavior)? I've seen it used before, but don't know the name of it.