Templated operation on type-erased type

Question

I have a template class val -

template <typename T>
class val;

This has the * operator overloaded for any pair of types T, T2. Basically a member -

template <typename T2>
void operator * (const val<T2>&);

Now I have another class val_holder that uses type erasure to hold val -

class val_holder;

template <typename T>
class val_holder_impl: public val_holder {
    val<T> m_val;
};

Finally in a separate class I have a template function that foo<T> that defines a val<T> x and receives as argument a val_holder* y.

I need to be able to invoke the * operator on x and the m_val inside the y.

I cannot use dynamic_cast because the template argument for y's precise type isn't known.

The other solution I tried is to have a virtual function in val_holder implemented by val_holder_impl<T> that invokes the * operator. But passing x would require the argument of the virtual function to be templated.

Any suggestions on how to get around this pattern?