• acotch shortbread,
• zcotch shortbread,
• xcotch shortbread,
• dcotch shortbread,
• ecotch shortbread,
• wcotch shortbread,
• sxotch shortbread,
• svotch shortbread,
• sfotch shortbread,
• sdotch shortbread,
• scitch shortbread,
• scktch shortbread,
• scltch shortbread,
• scptch shortbread,
• sc0tch shortbread,
• sc9tch shortbread,
• scorch shortbread,
• scofch shortbread,
• scogch shortbread,
• scoych shortbread

The adjective form of the phrase "Scotch shortbread" is "Scotch shortbread". However, the word "Scotch" in this context usually describes something or someone that is related to or originating from Scotland. Therefore, the phrase "Scotch shortbread" itself already functions as an adjective, describing shortbread that is associated with Scotland.

The plural form of "Scotch shortbread" is still "Scotch shortbread" as it is a compound noun that does not change when pluralized.

The singular form of the word "Scotch shortbread" is "Scotch shortbread". The word "Scotch" in this context is an adjective describing the type of shortbread, and "shortbread" is a noun referring to the sweet biscuit or cookie.