Minha avó gosta de cozinhar a mandioca com manteiga.

Because minha has to agree with avó, not with the speaker.

• avó = grandmother, a feminine noun
• meu = my, masculine singular
• minha = my, feminine singular

So:

• minha avó = my grandmother
• meu avô = my grandfather

This kind of agreement is very common in Portuguese.

They are different words:

• avó = grandmother
• avô = grandfather

The accent mark changes both pronunciation and meaning.

• avó has an open stressed vowel
• avô has a closed stressed vowel

So the accent is important here. Mixing them up changes who you are talking about.

Because the verb gostar normally requires the preposition de.

So in Portuguese, you do not usually say just:

• gosta cozinhar ❌

You say:

• gosta de cozinhar ✅

The same happens with nouns:

• Ela gosta de música.
• Ele gosta de café.

A good pattern to remember is:

• gostar de + noun
• gostar de + infinitive

Because after gostar de, when you talk about liking an action, Portuguese uses the infinitive.

So:

• gosta de cozinhar = likes cooking / likes to cook

You do not conjugate the second verb here:

• Minha avó gosta de cozinha ❌
• Minha avó gosta de cozinhar ✅

This is similar to English likes to cook or likes cooking.

That a is the feminine singular definite article, meaning the.

In Portuguese, articles are used more often than in English. With foods and everyday nouns, Brazilian Portuguese often sounds more natural with the article.

So:

• cozinhar a mandioca = cook the cassava
• cozinhar mandioca = understandable, but often less natural in this kind of sentence

Also, mandioca is a feminine noun, so the article is a, not o.

Mandioca is very common in Brazil, but Brazil also has regional names for the same food, especially:

• aipim
• macaxeira

These words can vary by region. In many places:

• mandioca is the broad, neutral term
• aipim and macaxeira are regional alternatives

So a learner should definitely know mandioca, even if local speakers may use another word in daily life.

By itself, com manteiga means with butter, but the exact idea depends on context.

It can suggest:

• butter is used during preparation
• the cassava is served with butter
• butter is part of the final dish

If you want to be more specific, Portuguese can say things like:

• cozinhar na manteiga = cook in butter
• servir com manteiga = serve with butter

So in your sentence, com manteiga is natural, but slightly broad.

Yes, people would understand you. But in Brazilian Portuguese, cozinhar a mandioca com manteiga usually sounds more natural.

Portuguese often uses articles in places where English does not. For a learner, it is often safer to include the article when talking about a specific food or dish like this.

So:

• cozinhar a mandioca com manteiga = more natural in many situations
• cozinhar mandioca com manteiga = possible, but a bit less typical here

It is completely natural.

Minha avó gosta de cozinhar a mandioca com manteiga follows a very common Portuguese pattern:

• subject: Minha avó
• verb phrase: gosta de cozinhar
• object: a mandioca
• extra detail: com manteiga

You can sometimes move parts around for emphasis, but this version is straightforward and normal.

A rough pronunciation for an English speaker is:

MEEN-ya a-VO GO-sta djee ko-zin-YAR a man-djee-O-ka kõ mahn-TAY-ga

A few useful notes:

• minha often sounds like MEEN-ya
• avó is stressed on the last syllable: a-VO
• de often sounds like djee in Brazilian Portuguese in connected speech
• cozinhar is stressed on -nhar
• nh is like the ny sound in canyon
• com has a nasal vowel, so it is not exactly like English comb
• manteiga is stressed on tei

You do not need perfect pronunciation right away, but paying attention to avó, de, and nh will help a lot.