Preheat your oven to 350°F/180 C
Butter a deep roasting tray or 2 baking sheets. Line the bottom with parchment paper. In a very large mixing bowl, combine all the dry ingredients.
In a bowl whisk together the melted butter and vanilla extract, eggs, and buttermilk till the liquid is frothy. Add the wet ingredients to the dry and mix with your hands to make sure all the flour is incorporated. Press the mixture into the baking tray and spread it evenly. Bake for 1 hour.
Lower your oven temperature to 190°F/ 90 C.
Remove the tray from the oven. Tip onto a large wooden board. Use a sharp knife to carefully cut into rusks. Place them onto 3 baking trays leaving space around the rusks for them to dry out. Bake them for 8 hours until completely dry. Store in an airtight container.
MAKES 60
Use a kitchen scale to measure. For gluten-free rusks use coconut/almond flour instead of whole wheat flour. I find using a kitchen scale helps with measuring all the ingredients
Find it online: https://melissamayo.com/recipe/healthy-museli-rusks/