Combine Dry Ingredients: In a medium bowl, whisk together the plain flour, bicarbonate of soda, and salt. Set this aside for later.

Cream Butter and Sugars: In a separate large bowl or the bowl of a stand mixer, beat the softened unsalted butter with the light brown sugar and caster sugar on medium speed for about 2-3 minutes, until the mixture is light, pale, and fluffy.

Add Wet Ingredients: Add the egg and vanilla extract to the butter mixture and beat again until just combined. Scrape down the sides of the bowl to ensure everything is incorporated.

Colour the Dough: Add 1 teaspoon of the blue gel food colouring and mix on low speed until the colour is evenly distributed. If you want a deeper, more intense blue, add a little more colouring until you reach your desired shade.

Combine Wet and Dry: Gradually add the dry flour mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix here. Finally, gently fold in the chocolate chips with a spatula.

Chill the Dough: This step is essential! Cover the bowl with cling film and refrigerate the cookie dough for at least 1 hour, or up to 24 hours. Chilling prevents the cookies from spreading too much in the oven. I find that a solid hour is the minimum for the best results.

Preheat and Prepare: When you're ready to bake, preheat your oven to 180°C (160°C fan) and line two large baking trays with parchment paper.

Assemble the Cookies: Scoop out a large ball of dough (about 2 tablespoons). Flatten it in your palm, place one mini chocolate chip cookie in the centre, and wrap the blue dough around it, rolling it back into a ball. Place the stuffed dough balls onto the prepared baking trays, leaving plenty of space between them as they will spread.

Bake to Perfection: Bake for 12-15 minutes, or until the edges are lightly golden and the centres look just set. They might seem slightly underdone in the middle, but they will continue to cook on the hot tray.

Add the Final Touch: As soon as you remove the cookies from the oven, gently press two googly eyes into the top of each warm cookie. Then, break one of the remaining mini cookies in half and stick it into the 'mouth' area. Let the cookies cool on the baking tray for 10 minutes before transferring them to a wire rack to cool completely.