Prepare Your Dry Ingredients: In a medium bowl, whisk together the 250g of plain flour, 1/2 tsp bicarbonate of soda, and 1/4 tsp salt. Set this aside for later.

Cream Butter and Sugars: In a large mixing bowl, using an electric hand mixer or a stand mixer with the paddle attachment, beat the 170g of softened unsalted butter and 150g of caster sugar on medium-high speed for about 3-4 minutes. You're looking for a light, pale, and fluffy consistency. This step, as explained by baking experts, incorporates air which is key to a good cookie.

Add Wet Ingredients: Add the large egg and 1 tsp of vanilla extract to the creamed butter mixture and beat again for another minute until everything is well combined. Scrape down the sides of the bowl to ensure it's all incorporated.

Combine Dry and Wet Mixtures: Pour the dry flour mixture into the wet ingredients along with the 85g packet of raspberry jelly crystals. Mix on a low speed until just combined. Be careful not to overmix; stop as soon as you no longer see streaks of flour.

Chill the Dough: Cover the bowl with cling film and place it in the refrigerator to chill for at least 30 minutes. This step is crucial for preventing the cookies from spreading too much while baking.

Preheat and Prepare: Towards the end of the chilling time, preheat your oven to 180°C (160°C fan). Line two large baking trays with baking parchment. Place the extra 50g of caster sugar in a small, shallow bowl.

Shape the Cookies: Remove the chilled dough from the fridge. Take about 1.5 tablespoons of dough and roll it into a ball between your palms. Roll the ball in the caster sugar to coat it completely, then place it on the prepared baking tray. Repeat with the remaining dough, leaving about 2 inches of space between each cookie ball. I find that using a cookie scoop ensures they are all a uniform size.

Bake to Perfection: Bake for 10-12 minutes. The cookies should look slightly puffed up and have set, slightly crinkled edges. They will still appear a little soft in the centre, which is exactly what we want for a chewy texture.

Cool Down: Let the cookies cool on the baking trays for 5 minutes before transferring them to a wire rack to cool completely. They will firm up as they cool.