Heat oven to 375°F. Line a baking sheet with parchment paper.
Combine wholemeal flour, all-purpose flour, salt, and baking soda in a large bowl, whisking to combine.
Pour buttermilk over dry ingredients, then coarsely grate butter over the buttermilk.
Stir to combine into a thick, somewhat gloppy mass, slightly damper than your average scone dough. If it doesn’t come together, add more buttermilk, 1 tablespoon at a time, until it does.
Dollop dough in four big mounds on prepared baking sheet and bake for 15 minutes, until just lightly golden brown at edges and dry to the touch.
Eat right away, split in half and spread with butter, jam, or chocolate.
