The phrase "a single portion or" is correct and usable in written English.
It can be used when discussing quantities, servings, or parts of a whole, often in contexts related to food, resources, or data.
Example: "You can choose a single portion or a family-sized meal depending on your needs."
Alternatives: "one serving or" or "a solitary piece or".
* When salting a single portion of meat or fish, salt all sides and be careful that the salt covers the meat evenly (the higher you hold your hand above the item being salted, the more evenly the salt will be distributed).
You can easily microwave one cob of corn, a potato, or a single portion of veggies.
A way to improve cost-effectiveness is to maximise the number of analytes that may be determined by a single procedure or from a single portion of test material, and/or to limit the sample pre-treatment steps.
A single portion of grain products like rice or pasta would be comparable to the size of your fist.
The game eases you in with simple orders, and steadily introduces new elements to ramp up the complexity — so you move from making up a single portion of chips, to making multiple fish & chips portions, with or without salt & vinegar, at the same time and so on.
3.4.2 Information on energy value should be expressed in kJ and kcal per 100 g or per 100 ml or per package if the package contains only a single portion.
3.4.3 Information on the amounts of protein, carbohydrate and fat in the food should be expressed in g per 100 g or per 100 ml or per package if the package contains only a single portion.
In general a single portion of fresh pasta in Italy is around 100 grams not the 300 or 400 grams you see in most Italian restaurants in Los Angeles". Angelo Auriana, chef and co-owner of the Factory Kitchen in downtown L.A. remembers having a conversation with a newly arrived Italian chef in San Francisco amazed at the size of the pasta portions in this country.
A single portion of charcoal to cook a meal costs at least 20 shillings (23 cents).
Like a Thanksgiving turkey, cassoulet brings people together by virtue of sheer volume; no one has ever made a single portion.
