Prima di infornare la pizza, aspetto che l’impasto lieviti bene.

Because after prima di when you mean before doing something, Italian normally uses an infinitive.

So:

• prima di infornare la pizza = before putting the pizza in the oven
• not prima di inforno la pizza, because inforno is a finite, conjugated form and does not fit after di here.

A useful pattern is:

• prima di + infinitive

Examples:

• Prima di uscire, chiudo la finestra.
• Prima di mangiare, mi lavo le mani.

If the subject changes, Italian often uses a full clause instead:

• Prima che la pizza entri nel forno...
  But in your sentence, the same person is doing both actions, so prima di + infinitive is the natural choice.

Infornare means to put into the oven.

It comes from forno = oven.

So:

• infornare la pizza = to put the pizza in the oven

It is not exactly the same as cuocere:

• infornare = putting something in the oven
• cuocere = cooking/baking it more generally

So this sentence is specifically about the moment before the pizza goes into the oven, not about the whole baking process.

Yes. Prima di infornarla is perfectly correct.

Both mean the same thing:

• Prima di infornare la pizza = before putting the pizza in the oven
• Prima di infornarla = before putting it in the oven

Here, -la is the direct object pronoun replacing la pizza.

The sentence with the pronoun is a little more compact and natural if la pizza is already clear from context.

So both are good:

• Prima di infornare la pizza, aspetto che l’impasto lieviti bene.
• Prima di infornarla, aspetto che l’impasto lieviti bene.

Aspettare che means to wait for / wait until something happens.

In this sentence:

• aspetto che l’impasto lieviti bene = I wait for the dough to rise well / I wait until the dough has risen properly

Italian often uses verb + che + clause where English may use a different structure.

Compare:

• Aspetto che arrivi. = I’m waiting for him/her to arrive.
• Aspetto che finisca. = I’m waiting for it to finish.

So aspetto che introduces the thing you are waiting to happen.

Because after aspetto che, Italian normally uses the subjunctive.

The verb is lievitare = to rise / to leaven.
Here, lieviti is the present subjunctive, third person singular.

Compare:

• Indicative: l’impasto lievita = the dough rises / is rising
• Subjunctive: aspetto che l’impasto lieviti = I wait for the dough to rise

This happens because aspettare che expresses something that has not happened yet, so Italian uses the subjunctive.

Similar examples:

• Spero che venga.
• Voglio che tu capisca.
• Aspetto che sia pronto.

Mostly, yes, or at least that is the most common everyday use.

Lievitare literally refers to rising, especially with dough, bread, pizza dough, and similar mixtures:

• L’impasto lievita. = The dough rises.

It can also be used more figuratively in other contexts, such as prices increasing:

• I costi sono lievitati. = Costs have gone up.

But in cooking, lievitare is exactly the right verb for dough rising.

Because impasto is a masculine singular noun, and normally it takes the article il:

• il impasto would sound awkward in Italian

So il becomes l’ before a vowel:

• l’impasto

This is called elision.

Other examples:

• l’amico from il amico
• l’uomo from il uomo

So:

• l’impasto = the dough

Here bene means something like well, properly, or enough.

So:

• l’impasto lieviti = the dough rises
• l’impasto lieviti bene = the dough rises properly / rises well

It adds the idea that the dough should rise sufficiently before baking.

In cooking Italian, bene is very common and often sounds natural where English might say:

• properly
• fully
• enough
• nicely

So the sentence is not just saying you wait for any rising at all, but for a good rise.

Because Italian usually does not need subject pronouns unless they are needed for emphasis or clarity.

The verb ending already shows the subject:

• aspetto = I wait
• aspetti = you wait
• aspetta = he/she waits

So aspetto already tells us the subject is I, and io is normally omitted.

You could say:

• Io aspetto che l’impasto lieviti bene

but that would usually sound more emphatic, like:

• I’m the one who waits
• As for me, I wait...

In a neutral sentence, leaving out io is normal.

Because Prima di infornare la pizza is an introductory phrase at the beginning of the sentence.

The comma helps separate:

• the time expression / introductory action from
• the main clause

So the structure is:

• Prima di infornare la pizza, = before putting the pizza in the oven
• aspetto che l’impasto lieviti bene. = I wait for the dough to rise properly

In short sentences, punctuation can vary a bit, but the comma is very natural and helpful here.

You could, but it would not mean exactly the same thing.

• infornare la pizza = to put the pizza into the oven
• cuocere la pizza = to cook/bake the pizza

Infornare focuses on the moment of placing it in the oven.
Cuocere refers more generally to the cooking process.

Since the sentence is about waiting for the dough to rise before the pizza goes into the oven, infornare is the more precise choice.

Not exactly.

• impasto = dough / mixture / batter-like mixture, depending on context
• pasta can mean pasta as food, or sometimes paste, but it is not the usual word for pizza dough in this sentence

For pizza, impasto is the standard word for the dough mixture before baking.

So:

• l’impasto della pizza = the pizza dough

Using pasta here would usually sound wrong or at least unnatural.

Yes.

Prima di can be followed by:

1. an infinitive

   • Prima di uscire, ti chiamo.
   • Prima di infornare la pizza...

2. a noun

   • Prima di cena, studio.
   • Prima della lezione, bevo un caffè.

So in your sentence, it is the first pattern:

• prima di + infinitive

That is why infornare stays in the dictionary form, not a conjugated one.