Melt butter and oil together in a heavy based saucepan over moderate heat. Add Ras el Hanout and cook gently for a minute or two, until fragrant.
Add chicken to spiced oil and brown quickly. Set aside.
Add onions to spiced oil and cook over moderate heat until softened and golden.
Return chicken to pot, add the sweet potato and stock to cover, stir to combine. Cover, bring to boil, then turn heat down to a slow simmer. Cook for 30 minutes.
Add chick peas and prunes and simmer for 10 minutes more, then stir in orange zest and simmer a further 5 minutes.
Serve on couscous, drizzling with a splash of orange blossom water and sprinkled with almonds.