Cream the butter and sugars. In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until the mixture looks light and fluffy—about 3 minutes with a hand mixer. The colour will turn a pale tan, and you'll smell the butter and sugar melding together. Scrape down the sides once.

Add the egg and vanilla. Crack in the egg and pour in the vanilla extract. Beat on medium speed until the mixture is smooth and glossy, about 30 seconds. The texture should look like thick cake batter at this point.

Combine the dry ingredients. In a separate small bowl, whisk together the flour, cinnamon, bicarbonate of soda, and salt. The cinnamon will release a warm, spicy aroma as you whisk.

Fold in the dry mixture. Add the flour mixture to the wet ingredients in two additions, stirring with a wooden spoon or spatula until just combined. You should see no white streaks of flour left. The dough will look shaggy and slightly sticky.

Stir in the oats and raisins. Tip in the rolled oats and raisins (and nuts if using). Fold until everything is evenly distributed. The dough will become stiff and chunky. You'll feel the oats adding resistance as you stir.

Chill the dough. Cover the bowl with cling film and refrigerate for at least 30 minutes. This is non-negotiable—the oats need time to absorb moisture. The dough will feel firm and cold to the touch when ready.

Preheat and prepare trays. Preheat your oven to 180°C (160°C fan). Line two baking trays with parchment paper. The paper should feel crisp and flat against the tray.

Scoop and shape. Use a tablespoon or cookie scoop to portion out balls of dough, about 1.5 tablespoons each. Roll them gently between your palms until smooth. Place them 5cm apart on the trays. They will look like small, neat domes.

Bake until golden. Bake one tray at a time for 10-12 minutes. The cookies will spread and crack on top. The edges should be golden brown while the centres still look slightly pale and soft. Your kitchen will smell like cinnamon and toasted oats.

Cool on the tray. Leave the cookies on the tray for 5 minutes. They will continue to set as they cool. The surface will firm up, and the bottoms will turn a deep golden brown. Transfer to a wire rack to cool completely.