What spices go with banana
Quick answer
Cassia, Allspice, Green cardamom — in roughly that order of how well established each combination is.
Each is explained below, with the cuisines it belongs to and the point at which it stops working.
Why banana behaves as it does
A green banana or plantain is a starch vegetable and is seasoned like one — salt, chilli, allspice, thyme across the Caribbean and West Africa. A ripe banana is dominated by isoamyl acetate, an ester so distinctive that it is what artificial banana flavouring is made of, and it takes the warm sweet spices: cassia, cardamom, nutmeg, and the Indian and Malay treatments with a fried banana. The one crossover is chilli, which works at both ends of the ripeness range for the same reason it works with mango and pineapple.
Classic
Long-established in at least one cuisine — the combinations you can rely on.
Cassia
ClassicFor the ripe fruit, and it is the pairing every fried-banana tradition arrives at from Southeast Asia to the Caribbean. Ripe banana is dominated by isoamyl acetate, an ester distinctive enough to be what artificial banana flavouring is made of, and cassia is one of few spices assertive enough to sit alongside it.
How: On fried banana; In banana bread
Strong
Allspice
StrongFor the green fruit rather than the ripe one, which is the distinction this pairing turns on. A green banana or plantain is a starch vegetable, and the Caribbean seasons it as one — allspice, thyme, salt and chilli — not as a fruit.
How: On fried or boiled green plantain
Good
Green cardamom
GoodThe South Asian treatment, and gentler than the cinnamon one. Cardamom's floral quality meets the banana ester rather than covering it, which suits a dessert where the fruit is supposed to remain identifiable.
How: In a banana halwa or milk drink
Cuts and forms
Ripe, Green, Plantain, Fried. These do not all take the same spicing — the notes above flag where the difference matters.