This is the 11649th most frequent Polish word.
kminku
"Kminku" is the genitive or dative form of "kmin," meaning "caraway" (a spice).
Here, 'kminku' is the genitive case of 'kmin' (cumin), used after the verb 'dodać' (add), which requires the genitive case for the object.
Nie zapomnij dodać kminku do chleba.
Don't forget to add cumin to the bread.
'Kminku' appears here in the genitive case after 'zamiast' (instead of), which governs the genitive.
Woli smak ziół zamiast kminku.
He prefers the taste of herbs instead of cumin.
Here, 'kminku' is in the genitive case used following the verb 'zawiera' (contains) in a contextual sense to ask about the presence of an ingredient.