Si la salsa queda demasiado fuerte, mi hermana añade menta fresca y sigue removiendo despacio.

Because this is a real or likely condition: If the sauce turns out too strong, my sister adds...

In Spanish, for this kind of general or possible condition, si is normally followed by the present indicative, not the subjunctive.

• Si la salsa queda demasiado fuerte, ... = If the sauce is / turns out too strong, ...
• Si tengo tiempo, voy. = If I have time, I’m going.

You do not use the future after si in this kind of sentence, so si la salsa quedará would be wrong here.

Quedar here means something like to turn out, to end up being, or to come out in a certain way.

So:

• La salsa está fuerte = The sauce is strong.
• La salsa queda fuerte = The sauce turns out strong / comes out strong.

In cooking, quedar is very common when talking about the final result of food:

• La sopa quedó salada. = The soup turned out salty.
• El pastel quedó seco. = The cake came out dry.

So queda emphasizes the result, not just the current state.

Here fuerte means strong in flavour, not physically strong.

With food, especially sauces, spices, garlic, alcohol, etc., fuerte often means:

• too intense
• too spicy
• too sharp
• too powerful in taste or smell

So la salsa queda demasiado fuerte means the sauce tastes too strong or too intense.

Because demasiado is modifying the adjective fuerte, so it normally goes before the adjective:

• demasiado fuerte = too strong
• demasiado caro = too expensive
• demasiado difícil = too difficult

Putting demasiado after the adjective would sound wrong in this structure.

Yes, both are possible, but añadir is very common in Spain, especially in recipes and cooking instructions.

• añadir = to add
• agregar = to add

In Spain, añadir often sounds a bit more natural in this context. In much of Latin America, agregar is also very common.

So:

• mi hermana añade menta fresca = my sister adds fresh mint

is perfectly natural Spanish from Spain.

Because in Spanish, when you talk about an ingredient in a general, indefinite way, you often do not use an article.

So:

• añade menta fresca = she adds fresh mint

This is similar to English, where you also usually say add fresh mint, not add the fresh mint, unless you mean some specific mint already mentioned.

If you were referring to specific mint, you could use an article:

• añade la menta fresca que compró ayer = she adds the fresh mint she bought yesterday

Seguir + gerund means to keep doing something or to continue doing something.

So:

• sigue removiendo = she keeps stirring / she continues stirring

This adds the idea that the action is ongoing.

Compare:

• remueve despacio = she stirs slowly
• sigue removiendo despacio = she keeps stirring slowly / continues stirring slowly

So the sentence is not just about one action, but about continuing the action after adding the mint.

Because after seguir meaning to continue, Spanish normally uses a gerund:

• seguir + gerund
• sigue estudiando = she keeps studying
• siguen hablando = they continue talking

So:

• sigue removiendo = she continues stirring

This is one of the most common uses of the Spanish gerund.

Both can relate to stirring or mixing, but remover is very common in Spain for stirring food.

In this sentence:

• remover = to stir

Examples:

• Remueve la sopa. = Stir the soup.
• Sigue removiendo. = Keep stirring.

Revolver can also mean to stir, but it can have other meanings too, such as to mix up, to rummage through, or to upset/disturb, depending on context. For a learner using Spain Spanish, remover is a very safe and natural choice in cooking contexts.

Both can mean slowly, but despacio is very common and natural in everyday speech.

• despacio = slowly
• lentamente = slowly, but often a bit more formal or literary

So:

• removiendo despacio sounds very natural in conversation and instructions.

You could say lentamente, but despacio is probably the more common everyday choice here.

Because the sentence expresses a habit, general practice, or recipe-like routine.

• queda
• añade
• sigue

These are in the present because the sentence means something like: Whenever the sauce turns out too strong, my sister adds fresh mint and keeps stirring slowly.

Spanish often uses the present tense for repeated actions and general truths, just like English:

• If it rains, we stay home.
• Si llueve, nos quedamos en casa.

Yes. Spanish often drops subject pronouns and even noun subjects when the meaning is clear from the verb or context.

So you could say:

• Si la salsa queda demasiado fuerte, añade menta fresca y sigue removiendo despacio.

That would still be grammatical if it is already clear that you are talking about my sister.

However, including mi hermana can help:

• make the sentence clearer
• introduce the person doing the action
• add emphasis or contrast

So the version with mi hermana is completely natural.

The word order is natural and standard:

• Si la salsa queda demasiado fuerte = condition
• mi hermana añade menta fresca = first action
• y sigue removiendo despacio = second action

Spanish word order is somewhat flexible, but this order is the clearest and most neutral.

For example, you could also say:

• Si la salsa queda demasiado fuerte, añade mi hermana menta fresca...

But that sounds much less natural in normal speech. The original sentence has the most straightforward word order for everyday Spanish.