kizi wo teppan ni hirogeru.

They mark the roles of the nouns in the sentence:

• 生地を = the dough/batter as the direct object
• 鉄板に = onto/on the iron plate, griddle, or baking tray as the destination/location

So:

• を answers what is being spread?
• に answers where is it being spread to?

That is why 生地を鉄板に広げる means something like spread the dough onto the tray.

Because に marks the place/resulting surface that something is spread onto.

• 鉄板に広げる = spread it onto the metal plate/tray

If you used で, it would usually mark the place where an action happens, more like at/on the tray as the setting. Here, the sentence focuses on the surface the dough ends up on, so に is the natural choice.

A useful way to think about it:

• に = target/destination/surface reached
• で = location where the action takes place

With 広げる, に is very common when something is spread onto a surface.

生地（きじ） often means dough, batter, or fabric, depending on context.

In a cooking sentence like this, it usually means:

• dough if it is thicker, kneaded, bread-like, pizza-like, etc.
• batter if it is more liquid, like pancake or crepe mixture

So the exact English translation depends on what is being made. Japanese often leaves that broader than English does.

鉄板（てっぱん） literally means iron plate, but in cooking it can refer to things like:

• a griddle
• a hot plate
• a metal baking tray
• a flat iron cooking surface

The best translation depends on the situation. In a recipe, it may mean the pan/tray/surface used for cooking or baking.

広げる（ひろげる） means to spread, to widen, or to open out something.

In this sentence, it means spreading the dough/batter out over the surface of the tray or plate.

It is a transitive verb, so it takes a direct object:

• 生地を広げる = spread the dough

Here the nuance is not just moving it, but making it cover more area.

Both can be translated as spread in English, but they are not exactly the same.

• 広げる = spread out, make cover a wider area
• 伸ばす = stretch out, roll out, extend, thin out

In cooking:

• 生地を広げる suggests spreading the dough/batter over a surface
• 生地を伸ばす often suggests rolling or stretching dough to make it thinner or longer

So if you are placing batter onto a tray and smoothing it outward, 広げる makes good sense. If you are flattening pizza dough with your hands or a rolling pin, 伸ばす is also common.

The dictionary form is very common in:

• recipe steps
• instructions
• captions
• informal written explanations
• plain-style statements

So 生地を鉄板に広げる。 sounds like a recipe instruction or procedural step.

A more polite version would be:

• 生地を鉄板に広げます。

But recipes often prefer the plain form because it is short and neutral.

Japanese often leaves out the subject when it is obvious from context.

In a recipe or instruction, the implied subject is usually:

• you
• or more loosely, the person following the recipe

So the sentence naturally means something like:

• (You) spread the dough onto the tray.

Japanese does this very often, especially in instructions.

Yes. Because particles show the grammatical role of each noun, Japanese word order is more flexible than English word order.

For example, these are all possible:

• 生地を鉄板に広げる。
• 鉄板に生地を広げる。

Both mean essentially the same thing. The difference is mostly one of emphasis or flow.

However, the verb usually comes at the end in a normal sentence.

It is pronounced:

きじ を てっぱん に ひろげる。

A few notes:

• 生地 = きじ
• 鉄板 = てっぱん
• 広げる = ひろげる

Notice that てっぱん has a small っ, which creates a brief pause before ぱ.

Yes, grammatically it is complete.

It has:

• an object: 生地を
• a target/location: 鉄板に
• a verb: 広げる

Even though Japanese omits the subject, that is perfectly normal. In context, especially in a recipe, this is a fully natural sentence.