Adding option to one product in Commerce but not to others of the same product type Ok so my situation is I am developing a website for a takeaway / restaurant and there are a number of products that fall under a product type, lets call this starters product type.

One of these products has the option for couscous or rice.

I would rather not have to list this as 2 listings on the menu and instead have it as one with some kind of option either before or after the person has clicked add to cart.

Are there any modules out there which are close to achieving something like this? Most I have found seem to be directed at product types as a whole.
You can build your restaurant menu based on views, where you list commerce_products instead of product types(nodes). This will render one row for each variation. 
You can also add relationship to your product types(nodes) for rendering/grouping/filtering.

You can also render the view of product variations at the product full page. Then the user will see all the possible variations of current product at once.