Learn Hardcore Indonesian: Kami menambah kecap sedikit agar tahu tempe lebih gurih. - We add a little soy sauce so the tofu and tempeh are tastier.

kami = we, not including the listener.
kita = we, including the listener. So kami implies the speaker’s group did this without including the addressee. In a recipe or demo directed at the reader/viewer, you’d often see kita (inclusive) or simply an imperative: Tambahkan kecap…

What’s the difference between menambah and menambahkan?

menambah X = to increase/add to the amount of X (focus on the thing being increased). Example: menambah kecap = add more soy sauce.
menambahkan X (ke/pada) Y = to add X to Y (explicitly marks the target). Example: menambahkan kecap ke sup = add soy sauce to the soup. In your sentence, either works. Many would say: Kami menambahkan sedikit kecap agar tahu dan tempe lebih gurih.

Is the placement of sedikit natural? Could I say sedikit kecap instead of kecap sedikit?

Both are natural, with a tiny nuance difference:

sedikit kecap treats sedikit as a quantifier (a little soy sauce).
kecap sedikit can read as an adverbial “add soy sauce a little (not much),” often used in speech. You’ll also hear the colloquial dikit: tambahin kecap dikit.

Does kecap mean ketchup?

No. kecap in Indonesian is soy sauce. Ketchup (tomato) is saus tomat. Common types:

kecap manis = sweet, thick soy sauce.
kecap asin = salty (light) soy sauce.
kecap inggris = Worcestershire sauce. When context doesn’t specify, many Indonesians default to kecap manis, but it varies by region/dish.

What does agar do here, and how is it different from supaya, biar, or untuk?

agar introduces a clause of purpose/result: “so that.” Near-synonyms:

supaya: very close to agar, slightly less formal.
biar: colloquial.
untuk: “for/to,” used with a verb phrase or noun, not a full finite clause unless you add untuk membuat…. All of these are fine with tone/register adjustments:
Formal: agar / supaya
Casual: biar

Do I need menjadi before lebih gurih?

No. agar tahu tempe lebih gurih is fully natural. Adding menjadi is optional and a bit heavier/formal: agar tahu tempe menjadi lebih gurih. Both are correct.

Should it be tahu tempe or tahu dan tempe?

Both are fine. tahu dan tempe is explicit. tahu tempe is a common pairing said as a set phrase meaning “tofu and tempeh,” especially in food contexts. You might also see a hyphen: tahu-tempe. None is wrong; choose by style and clarity.

What exactly does gurih mean?

gurih is “savory/umami,” often associated with a pleasant, mouth-filling savoriness (from salt, MSG, broth, coconut milk, fried shallots, nuts, etc.). It is not “spicy” (pedas) and not just “salty” (asin). lebih gurih = “more savory/umami.”

Can the subject kami be dropped?

Yes. Indonesian allows subject drop when context is clear:
Menambah kecap sedikit agar tahu tempe lebih gurih.
In instructions, imperatives are even more natural: Tambahkan sedikit kecap…

Why is it menambah, not something like menuang or memasukkan?

Different verbs emphasize different actions:

menambah/menambahkan: add/increase (quantity).
menuang: pour (focus on the pouring action).
memasukkan: put into.
mencampurkan: mix in.
You’d choose based on the action you want to highlight. Here, the idea is “adding (a bit more) soy sauce,” so menambah fits well.

What’s going on morphologically in menambah?

Root: tambah. The meN- prefix triggers sound changes: with roots starting in t, the initial t drops and the prefix surfaces as men-. So: meN- + tambah → menambah. The -kan suffix gives menambahkan (the applicative form).

How do comparatives like lebih gurih work? Where is “than …”?

Indonesian uses lebih + adjective for “more + adjective.” If you mention the standard of comparison, add daripada:

lebih gurih daripada yang tadi = more savory than earlier.
If context makes the comparison obvious (e.g., before vs. after adding soy sauce), lebih gurih alone is enough.

Is it better style to add -nya, like tahu-tempenya?

Adding -nya can mark definiteness or “that specific dish”:

agar tahu-tempenya lebih gurih ≈ so that the tofu-and-tempeh turns out more savory.
It’s optional and common when you refer back to something specific you’ve been cooking.

How might a native rephrase this in different registers?

Neutral: Kami menambahkan sedikit kecap supaya tahu dan tempe lebih gurih.
Instructional: Tambahkan sedikit kecap agar tahu dan tempe lebih gurih.
Casual: Biar tahu-tempenya lebih gurih, kita tambahin kecap dikit.
All are idiomatic; choose based on audience and tone.