Preheat the oven to 180°C/355F and grease two loaf tins, or vessels of your choice for the rusks. See notes.
Weigh out the flour, then add in the salt and baking soda. Whisk these ingredients to remove any lumps from the flour and to distribute the salt, baking soda and inherent leaveners throughout the flour.
1 kg self-raising flour, 2 teaspoon baking soda, 2 teaspoon table salt
Melt the butter in the microwave or on the stove-top. Add in the sugar and whisk vigoursly until the sugar is completely dissolved and the butter has thickened and is smooth and shiny. (this may take a minute or two). The butter and sugar may need to be heated for an additional 20 seconds or so to gain the correct consistency. Allow the butter to cool.
250 grams butter, 330 grams white granulated sugar
Whisk together the eggs and buttermilk.
600 grams buttermilk, 2 eggs
Add the butter and buttermilk mixtures to the flour and mix through with a wooden spoon or silicone spatula until combined. Then using your hands, knead the dough together a few times until you have a nice smooth-ish dough. We want a bit of gluten development but don't want bread dough.
To make chunky buttermilk rusks roll out golf-ball-sized pieces of dough and place in the loaf tins. To make sliced buttermilk rusks, divide the dough between your loaf tins and press into place. When making sliced buttermilk rusks, you can use a square cake tin or large roasting dish to bake your dough.
Bake the rusks - the balls or bolletjies or dough in a loaf tin take approximately 30 to 45 minutes to bake, while the large slice takes about 45 to 60 minutes to bake. But all ovens are different, the best bet would be to check the rusk using a toothpick or cake tester at the 30, 45, and 60-minute mark. When they come out clean, the rusk's first bake is complete.
Allow the rusks to cool before tearing apart or slicing them. When slicing rusks, I like to keep them about 2-3cm x 2-3cm big. Place the sliced or chunky rusks on the oven racks in the oven, and set your oven to a maximum of 110 degrees Celsius (cool oven), preferably with the fan on to dry the rusks out. This drying process can take anywhere from 2 to 5 hours depending on the thickness of your rusk. Rusks that are about 2-3cm x 2-3cm big tend to take about 2 hours to dry out while the chunky rusks take between 4 and 5 hours to dry out.