I think this works:
My hand is Horse Traders, Secret Chamber, Tunnel, Fools Gold, and Beggar.
My deck is Cultist, Trader, Dame Molly, Watchtower, and Market Square.
Opponent plays a Knight:
- Set aside HT (1)
- Play SC (2). Draw Cultist, Trader. Topdeck Cultist, Tunnel.
- Discard Beggar (3). I gain 2 silver, and use Trader (4) to regain the one that would have been topdecked to discard pile.
Opponent's Knight turns over Tunnel and Cultist
- Trashing the Cultist, letting me draw Dame Molly, WT, and MS
- Discard MS (5), gaining Gold (topdeck with WT (6))
- Discarding Tunnel (7), gaining Gold (topdeck with WT)
Opponent buys Province
- Trash FG (8 ), topdecking Gold.
My hand is now SC, Trader, Molly, WT. My deck is three golds; I have two silvers in discard.
- Return HT to hand, draw 1 gold.
- Play Molly (+2 actions)
- Play HT (+$3, discard SC, Trader)
- Play WT, drawing 2 gold (shuffle), 2 silver
- Play 3 gold, 2 silver; buy 2 province.
There's even room for one more card, so add a Hovel to the bottom of the deck, and trash it (9).