I used one of the alternative pastas (think it was edamame bean) which folk won't notice in the recipe I used last night. Nicked from the Cafe Fish in Tobermory. Its a tasty variant on Macaroni Cheese. You will need a extra strong mature cheddar. They used Isle of Mull cheese, which has a unique taste because it's made with unpasteurised milk.
First off, poach a couple of smoked haddock fillets in milk for around 6 minutes, just long enough to allow you to flake the fish.
Use that milk to make a cheese sauce the usual way ( you may need to add more milk) and check the seasoning.(I added freshly ground white pepper. You won't need much salt, if any because of the cheese and fish) While that is being created, get the pasta cooking, and stop cooking it about 2/3 of the recommended time.
Put the cooked pasta in a roasting dish that's presentable at the table, pour the cheese sauce on the pasta (which should be either tubular or shell shaped) and stir in the smoked haddock flakes.
Spread Panko breadcrumbs on the top, and grated Parmesan or similar across the top, and stick it in the oven at around 200 centigrade (fan 180) until the breadcrumbs are turning golden, then serve it up.
The carbs are in the flour for the cheese sauce, the low carb pasta and the breadcrumbs. Using normal pasta would send the carbs sky high, as I discovered in the Cafe Fish, fortunately forestalled by a big whack of insulin.
Why add the breadcrumbs? Its the crunchy mouthfeel that contrasts with the softness of the pasta mix. You don't need to add that stage at all, the pasta sauce is quite tasty enough on its own, it's simply a cheffy touch and not vital, just my addition to the Cafe Fish recipe.
If you do the whole thing, it will take around 40 minutes to complete if you get your multi tasking just right, and preheat the oven. If you aren't doing the oven bit, you can can do it in less than half an hour but cook the pasta the full recommended time.