The mother is also from Meknes, and she makes it the same way as you do, but she doesn't use butter because she keeps the zmita or slo for a month and a half of Ramadan or more, and when butter is kept for a long time, it gives an undesirable taste. That's why she replaces butter with Willow oil that is free of cholesterol, along with oud oil.
ﺍﻟﻮﺍﻟﺪﺓ ﻣﻜﻨﺎﺳﻴﺔ ﺣﺘﻰ ﻫﻲ ﺍﺑﺎ ﻋﻦ ﺟﺪ ﻛﺎﺗﺪﻳﺮ ﻧﻔﺲ ﻃﺮﻳﻘﺘﻚ ﺍﻻ ﺍﻧﻬﺎ ﻻ ﺗﺴﺘﻌﻤﻞ ﺍﻟﺰﺑﺪﺓ ﺑﺴﺒﺐ ﺍﻥ ﺯﻣﻴﺘﺎ ﺍﻭ ﺳﻠﻮ ﺗﺤﺘﻔﺾ ﺑﻬﺎ ﻟﻤﺪﺓ ﺷﻬﺮ ﺭﻣﻀﺎﻥ ﻭﻧﺼﻒ ﻣﻦ ﺷﻮﺍﻝ ﺍﻭ ﺍﻛﺜﺮ ﻭﺍﻟﺰﺑﺪﺓ ﻋﻨﺪ ﻃﻮﻝ ﺍﻟﻤﺪﺓ ﺗﻌﻄﻲ ﻣﺬﺍﻕ ﺍﺧﺮ ﻏﻴﺮ ﻣﺮﻏﻮﺏ ﻓﻴﻪ ﻟﻬﺬﺍ ﺗﻌﻮﺽ ﺯﺑﺪﺓ ﺑﺰﻳﺖ ﻭﻳﻠﻮﺭ ﺧﺎﻟﻲ ﻣﻦ ﻛﺎﺳﺘﺮﻭﻝ ﻣﻊ ﺯﻳﺖ ﺍﻟﻌﻮﺩ