Having trouble deriving MMonad for monad stacks

Given some random transformer stack, where all of the transformers implement `MMonad`:
```
newtype FooT m a = FooT { unFoo :: ExceptT () (StateT Int (BarT m)) a }
```

I'm finding it difficult to create instances of `MMonad` for `Foo`, without just running everything and manually implementing `embed` for the entire stack.

Am I missing something, or is this because monads don't compose? Is there an equivalent of monad transformers for the category of monads? Maybe that would make creating these instances easier.

Any thoughts appreciated, hopefully I'm just missing something obvious.