Creamy Fish With Mushrooms and Bacon

depending on thickness, diced

or white, stems discarded and caps halved or quartered

large, diced

or chicken

plus more for fish and to taste

finely ground, plus more for fish

or heavy cream

more for garnish

fluke, tilefish, hake or other white fish, 1 1/4 to 1 1/2 pounds ), skin removed

or buttered toast, for serving