Do you ever use “a”/an in front of food when you order it in a restaurant?

I hope you can have a look at the following orders and tell me whether or not they sound better with the indefinite article. Thank you.

I'll have ...
pasta with clams and mussels/tomato sauce/ meat sauce/ butter and sage/gravy
grilled/fried/roast chicken breast (roast leg of lamb, a grilled sirloin steak, a hamburger, a breaded cutlet, rabbit stew, braised beef etc..)
a poached/fried/soft-boiled/hard-boiled egg
cod/plaice/fried sole with spinach/carrots /courgettes/ cauliflowers/ asparagus/ spinach/ fennels/ peas/ roast/mashed/boiled potatoes/chips/ beetroots/ red cabbage/ Brussels sprouts/ French beans/ beans ….
a Half-a-litre bottle of fizzy water
some grapefruit juice.

The article "a" or "an" is used when you are specifically referring to ONE thing:

a piece of steak

a cup of coffee

a hard-boiled egg

But when referring to something you cannot count (such as coffee, cereal, pasta), then the article is not used.

Basically, you're dealing with "count and non-count nouns" --
http://leo.stcloudstate.edu/grammar/countnon.html
and
http://grammar.ccc.commnet.edu/grammar/noncount.htm

Let me know if you have more questions.

When ordering food in a restaurant, the use of indefinite articles "a" or "an" may vary depending on the context.

Here are some guidelines to help you decide when to use the indefinite article:

1. For specific dishes or items:

- If you are ordering a specific dish, it is more common to omit the indefinite article. For example:
"I'll have pasta with clams and mussels." (No indefinite article)
"I'll have cod with spinach." (No indefinite article)

- However, if you want to emphasize the type of ingredient or preparation method, you can use the indefinite article. For example:
"I'll have a pasta with tomato sauce." (Emphasizing the type of sauce)
"I'll have a grilled sirloin steak." (Emphasizing the preparation method)

2. For general categories or quantities:

- When referring to a general category of food, it is common to use the indefinite article. For example:
"I'll have a fried sole with spinach." (Referring to any fried sole)
"I'll have a plate of mashed potatoes." (Referring to any mashed potatoes)

- When referring to a quantity of a specific item, you can use the indefinite article. For example:
"I'll have a half-liter bottle of fizzy water." (Referring to a specific quantity)
"I'll have a grapefruit juice." (Referring to a specific glass of juice)

Remember that these guidelines can vary depending on regional preferences and individual style. If you are unsure, you can observe how others order or ask the restaurant staff for their recommendations.