Preheat your oven to 180°C (160°C fan) and line a baking tray with parchment paper. While it heats, combine the almond flour, coconut flour, granulated sweetener, baking powder and salt in a large bowl. Whisk briefly with a fork until the mixture looks uniformly pale and there are no clumps of coconut flour – you'll see it lighten in colour as the powders integrate.

Drop in the cold butter cubes and cut them into the flour mixture using a pastry cutter or two forks. Work quickly so the butter stays cold – you're aiming for a texture that resembles coarse breadcrumbs, with some pea-sized butter lumps still visible. If the mixture starts to look greasy or clings together, you've overworked it; pop the bowl in the fridge for five minutes.

Stir in the beaten egg, double cream and vanilla extract with a silicone spatula until a soft, slightly tacky dough forms. It should feel cool to the touch and hold together when pressed between your fingers, but not be wet or sticky. If it crumbles, add another teaspoon of cream; if it's too wet, dust in a tablespoon more almond flour.

Turn the dough out onto a sheet of parchment paper and pat it into a disc about 2cm thick. Use the 6cm cutter to stamp out rounds – you should get six from the first press. Gather the scraps gently, re-pat and cut again without overworking; you'll smell the butter and vanilla as you handle it, which tells you the dough is fresh.

Place the rounds on the lined baking tray, spaced about 3cm apart. They won't spread much, but leaving space ensures even browning. Bake for 16 to 18 minutes – the tops should turn a deep golden brown and the edges will look slightly darker. A gentle press with your fingertip should feel firm, not squishy, and the kitchen will smell richly of toasted almond and vanilla.

Transfer the shortcake discs to a wire cooling rack and let them cool completely. This takes about 30 minutes. Don't rush this step – warm shortcake will melt your cream and turn the whole thing into a sad puddle. While they cool, whip the remaining 300ml double cream with the powdered sweetener and lemon zest until soft peaks form; you're looking for a texture that holds its shape when you lift the whisk, but still looks silky and smooth.

To assemble each cup, drop one shortcake disc into the bottom of a serving glass. Spoon over a layer of sliced strawberries, then a generous dollop of whipped cream. Repeat with a second disc, more berries and a final cream swirl on top. You'll see the red strawberry juice bleed gently into the white cream – that's exactly what you want for visual appeal.