negi to toriniku wo tukatta suupu ha, yoru de mo tabeyasui desu.

No. ねぎ と 鶏肉 works as one combined noun phrase: green onion and chicken.

So:

• ねぎ と 鶏肉 を 使った
• literally: used green onion and chicken

The を marks the whole thing as the object of 使った, not just 鶏肉 by itself.

So this part is understood as:

• [ねぎと鶏肉]を使った
• made using green onion and chicken

Here, 使った is describing スープ.

Japanese often puts a verb directly before a noun to modify it. This is called a relative clause.

So:

• ねぎと鶏肉を使ったスープ
• soup that uses / soup made with green onion and chicken

A very literal breakdown is:

• ねぎと鶏肉を使った = used green onion and chicken
• スープ = soup

Together: the soup that used green onion and chicken → more natural English: soup made with green onion and chicken

This is a very common learner question.

In Japanese, a past form inside a noun-modifying clause does not always mean the whole sentence is in the past. Here, 使った shows a completed action relative to the noun:

• the ingredients have already been used in making the soup

So ねぎと鶏肉を使ったスープ means:

• a soup made with green onion and chicken

This is similar to English made with. It does not mean the soup was easy to eat in the past. The main sentence is still present because of 食べやすいです.

は marks スープ as the topic of the sentence.

So the structure is:

• ねぎと鶏肉を使ったスープは、
  As for soup made with green onion and chicken, ...

Then the rest says something about that topic:

• 夜でも食べやすいです
  it is easy to eat even at night

So は is not marking the subject in exactly the same way English does. It is setting up what the sentence is about.

夜でも means even at night.

Here, でも is functioning like even when attached to a noun.

So:

• 夜 = night
• 夜でも = even at night

It is best to learn this as a chunk here rather than as 夜 + で + も in the English sense.

The nuance is:

• this soup is easy to eat
• not only in general, but even at night, when heavier food might feel less suitable

食べやすい means easy to eat.

It is made from:

• 食べる = to eat
• やすい = easy to do

So:

• 食べやすい = easy to eat
• 飲みやすい = easy to drink
• 分かりやすい = easy to understand

This is different from 食べられる, which usually means:

• can eat
• is edible
• can be eaten

So compare:

• 食べやすい = easy to eat, not heavy, not difficult, goes down easily
• 食べられる = possible to eat

In this sentence, 食べやすい suggests the soup feels light, gentle, or not burdensome, especially at night.

Yes. That is completely normal.

食べやすい behaves like an い-adjective, and in polite speech you can say:

• 食べやすいです

This is the standard polite form.

Compare:

• plain: 食べやすい
• polite: 食べやすいです

You do not say:

• 食べやすいだ ✘

That is incorrect.

It often implies more than literal ease of chewing or swallowing.

With food, 食べやすい can mean:

• easy to eat physically
• mild in flavor
• not too heavy
• suitable when you do not want something rich or intense

So 夜でも食べやすい suggests:

• it is light or gentle enough that it still feels appropriate at night

This is a very natural kind of nuance in Japanese food descriptions.

Yes, you could say ねぎと鶏肉のスープ.

The difference is nuance:

• ねぎと鶏肉のスープ = green onion and chicken soup
• ねぎと鶏肉を使ったスープ = soup made using green onion and chicken

The version with を使った sounds a little more descriptive and explicit about the ingredients being used. It can feel slightly more explanatory or promotional, like menu language or food writing.

The の version is shorter and more straightforward.

Yes, from an English point of view, the sentence has an understood subject.

Japanese often leaves out things that are clear from context. After スープは, the sentence does not need to repeat it.

So:

• ねぎと鶏肉を使ったスープは、夜でも食べやすいです。

Literally:

• As for the soup made with green onion and chicken, easy to eat even at night.

Natural English supplies it is:

• Soup made with green onion and chicken is easy to eat even at night.

Yes, it is natural.

A normal written form would be:

• ねぎと鶏肉を使ったスープは、夜でも食べやすいです。

The spaces in your version are just for learners. In ordinary Japanese, spaces are usually not used like that.

The sentence sounds like something you might see in:

• a recipe description
• a menu comment
• a food blog
• a health-conscious food recommendation

It has a gentle, descriptive tone.