A few years ago I started grating or shredding some of the zucchini at the start of a summer risotto. The shreds fell apart and melted into the rice and cooking liquid, giving the dish a somewhat thickened consistency. Then, a minute before the risotto was done, I'd add diced skin-on zucchini -- either quickly sautéed or not -- which would then remain slightly crisp and totally fresh-tasting. (I might have picked this up from a friend's restaurant, but I'm not sure.)
More recently, I extended this to winter squash/pumpkin risottos as well, and it worked even better because the denser flesh of something like a butternut squash really did make the risotto creamy (think of the consistency of a puréed pumpkin soup). But I still added chunks of seared or roasted squash toward the end to add a textural contrast. Note that for risotto purposes I use squash and pumpkin interchangeably: buy whatever looks good in the market and, when opened, has a nice fruity aroma.
The other day Jackie said that the remains of a loaf of delicious bread should be made into croutons, which was an excellent idea. These (slowly crisped in butter or olive oil with a clove of garlic and maybe some herbs to perfume them) are a fine snack and an almost optimal topping for anything that needs a boost of crunch: pasta dishes, vegetable gratins ... and risottos. Aha! If appealing texture is going to come from the croutons, why not skip the chunks of pumpkin/squash altogether?
That's what I did using half a smallish kabocha squash. After cutting it into wedges, peeling it and removing the seeds and pith, I shredded it on the coarse side of a box grater. (Note the order of battle: cut it into wedges before peeling it. Especially with a hard squash, it is much safer to lay a smaller piece on the cutting board and remove the skin with a knife.)
In the broad but fairly deep pan I use for risotto -- like this one, but heavier, older and uglier -- I sweated a couple of big shallots, minced, in butter (onions would be fine, but I'm on a shallot binge), then added all of the shredded squash -- a good two cups of it -- seasoned with salt, pepper and chopped rosemary. I stirred this around until aromas became apparent and the squash was just beginning to soften, then added 2/3 cup carnaroli rice (for two portions) and cooked this with the squash for a minute or two. Yes, I know: many people think that frying the rice in the butter / oil is crucial to making a good risotto. I'm not sure I agree.
From here on, the risotto proceeded as usual, with the addition and reduction of about a quarter cup of white wine, then successive additions of heated vegetable stock and pretty much constant, moderately vigorous stirring. The stirring is particularly important here because you want to break down the squash as it softens. Toward the end of the cooking time, when the rice was very nearly done, the saucy part of the dish was creamy (the starch from the rice was a factor here, too) and the few remaining fragments of squash were incidental. Remember to use plenty of liquid, whether it be vegetable stock, diluted chicken stock or plain salted water: you want your risotto to move around when you tilt the plate and you want plenty of squash-puree-thickened sauce in every spoonful. I finished the risotto with a couple of tablespoons each of grated parmesan and butter, vigorously stirred in to create a nice creamy liaison. After a taste, I squeezed in the juice of a quarter of a lemon: clearly, the wine hadn't provided enough acidity.
I scattered croutons (also rosemary-scented) on top of each portion just before serving. The result was such a pleasure to eat: all that squash flavor in and around the rice, and a real night-and-day contrast provided by the noisily crunchy croutons.
Come summer (not yet, please!), I'll try this with zucchini too -- with the added benefit of not having to cut the flesh into those perfect 1/4-inch dice that everybody expects nowadays.