Preheat the oven to 180°C.
Grease 3 to 4 loaf tins or one large rectangular oven pan.
Melt the butter and let it cool down for a few minutes.
Sift the dry ingredients together in a large mixing bowl.
Add the sugar, bran cereal and seed mixture and stir through the dry ingredients.
Add the beaten eggs and vanilla essence to the buttermilk and mix.
Add the buttermilk mixture and the melted butter to the dry ingredients and mix very well or use a stand mixer with the K-paddle attachment. * See note
Spoon the dough into your prepared tins or pans and flatten it by hand.
Bake for 30 - 40 minutes until a skewer inserted in the middle comes out clean.
Let the rusks cool down before you cut them into fingers or squares.
Place the rusks on baking sheets with some space around each rusk and dry them in a cool oven (65 - 90°C) for 5 to 6 hours or overnight. Leave the oven door slightly open to aid the drying process.