Prepare the shortcake base. Preheat your oven to 180°C (160°C fan). Line a 20cm x 20cm square baking tin with a strip of parchment paper, leaving an overhang on two sides. In a large bowl, whisk together the flour, caster sugar, baking powder, and salt. Drop in the cold butter cubes and rub them into the flour mixture using your fingertips until it looks like coarse breadcrumbs — pale yellow and sandy in texture, with no large butter lumps remaining.

Bring the dough together. Make a well in the centre and pour in the double cream, beaten egg, and vanilla extract. Stir with a wooden spoon until the dough just comes together. It will feel soft and slightly sticky. Press this dough evenly into the bottom of your prepared tin. The surface should feel smooth and level under your fingers.

Bake the shortcake. Place the tin in the oven and bake for 18–20 minutes. The shortcake is ready when the edges are a deep golden brown and the centre springs back when you press it gently. A lovely toasty, buttery aroma will fill your kitchen. Transfer the tin to a wire rack and let the shortcake cool completely — about 30 minutes.

Layer the ice cream. Once the shortcake is cool, spoon the softened strawberry ice cream over the top. Spread it into an even layer using the back of a spoon or an offset spatula. The ice cream should be smooth and creamy, reaching right to the edges of the tin. Press the sliced strawberries gently into the ice cream, arranging them in a single layer. The berries will look glossy and bright against the pale pink ice cream.

Make the whipped cream topping. In a chilled bowl, pour the double cream, icing sugar, and vanilla bean paste. Whisk with a hand mixer on medium speed until soft peaks form — the cream should hold its shape when you lift the beaters, but still look silky and smooth, not stiff or grainy. Spread this whipped cream over the strawberry layer, right to the edges. The top should look cloud-like and billowy.

Freeze until firm. Place the tin in the freezer, uncovered, for at least 4 hours or overnight. The bars need to be completely solid. When you press the top, it should feel firm and unyielding, with no give at all.

Slice and serve. Lift the whole block out of the tin using the parchment overhang. Place it on a cutting board. Use a sharp, heavy knife to slice the block into 12 even bars. The first cut will feel satisfyingly clean, revealing the layers of golden shortcake, pink ice cream, red strawberries, and white cream. Serve immediately, straight from the freezer.