yangpareul jakge sseoreoseo bokkayo.

Because 작게 is the adverb form of 작다 (to be small), and it describes how the onion is cut.

• 작은 양파 = a small onion
  
  • Here, 작은 modifies the noun 양파
• 양파를 작게 썰어요 = cut the onion small / into small pieces
  
  • Here, 작게 modifies the verb 썰어요

So in this sentence, the idea is not that the onion itself is small, but that you cut it into small pieces.

썰다 usually means to slice, to chop, or to cut up food, especially with a knife.

자르다 is a more general word meaning to cut. It can be used for food, paper, string, hair, and many other things.

So:

• 자르다 = general cut
• 썰다 = slice/chop food into pieces

In cooking sentences, 썰다 is very common because it sounds more natural for ingredients like onions, carrots, and meat.

-어서 / -아서 connects two actions. Here it means something like:

• cut it, and then
• after cutting it

So:

• 썰어서 볶아요 = cut it and fry it

In recipe language, this often shows a natural sequence of actions. First you cut the onion, then you stir-fry it.

The object marker 를 appears with 양파 once, and that object is understood with both verbs.

So the sentence is basically:

• 양파를 작게 썰어서 (양파를) 볶아요

The second 양파를 is omitted because Korean often leaves out repeated words when they are obvious.

This is very common and natural.

In Korean, the present polite form is often used for:

• instructions
• recipes
• directions
• general procedural steps

So 볶아요 literally looks like stir-fry in present tense, but in context it means something like:

• stir-fry it
• then stir-fry it
• you stir-fry it

This is a very normal way to write cooking instructions politely.

It is grammatically in the -아요 polite style, which can sound like either:

• a polite statement, or
• a soft instruction

In recipe context, it is usually understood as an instruction:

• Cut the onion into small pieces and stir-fry it.

If you wanted a more direct command, you might see:

• 썰어서 볶으세요

But -아요 is extremely common in recipes because it sounds natural and friendly.

There is no explicit subject, and that is normal in Korean.

In a recipe, the subject is usually understood as:

• you
• or a general instruction to whoever is cooking

Korean often omits subjects when they are obvious from context.

So this sentence does not need you stated explicitly.

Because Korean adverbs usually come before the verb they describe.

Here:

• 작게 describes 썰다
• so it comes before 썰어서

This is similar to English cut it finely, where finely describes cut.

Korean word order is often:

• object + adverb + verb

So:

• 양파를 작게 썰어서 볶아요

is a very natural order.

It is similar, but not always exactly the same.

작게 썰다 means:

• cut into small pieces
• chop small

Depending on context, English might translate it as:

• chop finely
• cut into small pieces
• dice finely

But Korean 작게 썰다 is a bit more general than the English cooking term finely chop. It simply tells you the pieces should be small.

Yes, you can, and it would still make sense.

• 썰고 볶아요 = cut it and fry it
• 썰어서 볶아요 = cut it and then fry it / after cutting it, fry it

The difference is subtle:

• -고 simply links actions
• -어서 often feels a little more like one action leads into the next

In a cooking instruction, 썰어서 볶아요 sounds very natural because the first action naturally comes before the second.

볶아요 is in the polite informal style, often called the -아요/어요 style.

It is:

• polite
• common in everyday speech
• very common in recipes, tutorials, and instructions

It is less formal than:

• 볶습니다

and less direct than:

• 볶아라 or 볶아

So it gives the sentence a friendly, standard polite tone.