Es mejor que laves bien las espinacas y los champiñones antes de ponerlos en la sartén.

Because es mejor que normally triggers the subjunctive in Spanish.

Here, laves is the present subjunctive form of lavar for tú. The sentence is giving advice or a recommendation, not just stating a fact, so Spanish uses the subjunctive:

• Es mejor que laves... = It’s better that you wash...
• Lavas would be indicative, which does not fit naturally after es mejor que in this kind of sentence.

A very common pattern is:

• Es bueno que...
• Es importante que...
• Es mejor que...

and then a subjunctive verb after that.

Spanish often omits subject pronouns because the verb ending already shows who the subject is.

Here, laves already tells you the subject is tú. So tú is understood:

• Es mejor que laves...
• Es mejor que tú laves...

Both are possible, but the version without tú is more natural unless you want extra emphasis or contrast.

Yes. That is also correct, but the structure is slightly different.

• Es mejor que laves... directly addresses you
• Es mejor lavar... is more general, like saying It’s better to wash...

So:

• Es mejor que laves bien las espinacas... = It’s better that you wash the spinach well...
• Es mejor lavar bien las espinacas... = It’s better to wash the spinach well...

Both are natural, but the version with que + subjunctive sounds more like advice aimed at a specific person.

Because Spanish uses definite articles much more often than English, especially with food items, ingredients, and nouns being talked about in a general or practical way.

So Spanish naturally says:

• las espinacas
• los champiñones

where English often just says spinach and mushrooms without an article.

This is very common in recipes and kitchen instructions.

In Spanish, espinacas is very commonly used in the plural when referring to spinach as a food ingredient. That is just the normal idiomatic way to say it in many contexts.

So even though English treats spinach as an uncountable noun, Spanish often uses:

• las espinacas

This does not necessarily mean separate individual spinach plants; it is simply the usual way to talk about spinach in cooking.

Because poner is an infinitive, and object pronouns can be attached directly to infinitives in Spanish.

So:

• poner + los = ponerlos

This los means them.

Spanish allows object pronouns to attach to:

• infinitives: ponerlos
• gerunds: poniéndolos
• affirmative commands: ponlos

In this sentence, antes de is followed by an infinitive, so ponerlos is a very natural structure.

Because the pronoun refers to both las espinacas and los champiñones together.

When Spanish refers back to a mixed group containing at least one masculine noun, it normally uses the masculine plural pronoun:

• las espinacas = feminine plural
• los champiñones = masculine plural
• together = los

So ponerlos means to put them, referring to both ingredients together.

If the pronoun referred only to espinacas, then ponerlas would be correct.

Because antes de is followed by an infinitive when the subject is the same.

In this sentence, the person who washes the vegetables is also the person who puts them in the pan, so Spanish uses:

• antes de ponerlos

If the subject changes, Spanish usually uses:

• antes de que + subjunctive

For example:

• Es mejor que laves las espinacas antes de que tu hermano las ponga en la sartén.

So the rule is roughly:

• same subject → antes de + infinitive
• different subject → antes de que + subjunctive

Because adverbs like bien usually come after the verb in Spanish.

So:

• laves bien = wash well

That is the normal order. English and Spanish are similar here, although Spanish word order is often a bit more flexible.

In this sentence, bien means something like properly or thoroughly.

Because with poner, Spanish normally uses en to mean put into / in / on a container or surface such as a pan.

So:

• ponerlos en la sartén = put them in the pan

Using a would not sound natural here with poner.

Also, la sartén is the common form in Spain. The noun sartén can be masculine or feminine in some varieties, but la sartén is very common and standard, especially in Spain.

Not exactly.

In Spain:

• champiñones usually means the common cultivated mushrooms, especially button mushrooms
• setas is a broader word for mushrooms in general, often including wild mushrooms

So champiñones is more specific than setas.

In this sentence, champiñones suggests ordinary cooking mushrooms, the kind you would commonly wash and fry in a pan.