I get a really nice texture in the tofu by par-boiling cubed firm tofu for about three minutes in a large quantity of water, draining the cubes well before proceeding with the recipe. I have found this step produces cubes whose outsides resist crumbling when you stir them around in the sauce (though of course you still have to stir them gently!), and whose insides are soft and almost fluffy.
I think what mizducky used already has texture. The tofu cubes look firm, but I'll bet the inside is silky smooth.
Plus I chop my fermented black beans rather than mashing them, so there's texture from that too.