To whom is the Duke speaking in "My Last Duchess"?

Part of the mastery of Browning's art in this poem is that we
are only told who the audience of the Duke's dramatic monologue is at the end of the poem, after
he has seemingly quite cheerfully narrated how he had his "last Duchess" disposed off because of
how, in his perception, she bestowed attention of others. Thus, having established the immense
pride and cruelty of the Duke, it is highly ironic that we discover in the last few lines that
the silent listener is a representative from a Count whose Duke the daughter is negotiating to
marry:

The Count your
master's known munificience

Is ample warrant that no just
pretense

Of mine for dowry will be
disallowed;

Though his fair daughter's self, as I
avowed

As starting, is my
object.

Now, when we think about this,
this is either incredibly ironic or/and it is incredibly chilling. Either we think that the Duke
has no awareness of what the story of his last Duchess is doing to the listener, or, he is
deliberately sending a message to the Count about the kind of behaviour he expects from a wife
and the kind of response he can expect if his daughter does not behave
accordingly.