What interpretation actually gives the Catholic Priests the ability to perform these miracles at will? Even Christ was quick to say that of Himself he was nothing as it was the Father that doeth the works...
You said: What interpretation actually gives the Catholic Priests the ability to perform these miracles at will?
The premise of your question is wrong. I sense you are misinformed. Catholic priests do no perform miracles.
During the Mass (and Divine Liturgy in the eastern Church), it is Christ who changes bread and wine into His body, blood, soul and divinity, as He did at the Last Supper. It is a sacramental representation of the once and for all sacrifice.