What about making it a cantrip (and making the trashing optional, but a requirement for matting it)? That makes it stronger as a one-shot trasher, and keeps it from being a Confusion after you call it.
Investment - Action-Reserve
+1 Card
+1 Action
Trash up to 2 Treasures from your hand. If you trashed a Treasure this way, put this on your Tavern mat.
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When you gain a Province, you may call this, to gain a Gold, putting it on top of your deck.
I think "Trash up to 2 Treasures" is better than "You may trash 2 Treasures" because the latter causes ambiguity about what should happen if you only have one Treasure in your hand (Can you choose to trash 2 Treasures and then fail to fully carry it out? What keeps you from lying about only having one Treasure when you have, say, a Copper that you want to trash and a Gold that you don't?).
This does let you trash a Copper/Silver for a Gold next turn if you play it on a turn when you buy a Province, but I'm not sure that's overpowered (compare it to Taxman).