Preheat the oven to 350 degrees. Line a baking sheet with parchment paper.

In a medium bowl, sift together the sugar, oats, flour and salt.

Add the unsalted butter, using your fingers to combine it all together until incorporated enough that it forms clumps.

Using your fingers, place the oat mixture clumps onto the parchment paper, spreading out evenly.

Bake for 15-20 minutes until toasty and browned. Let cool completely before using.

In the bowl of a stand mixer with the beater attachment, whip the mascarpone, icing sugar and lemon zest on high to give it some volume.

Turn off the mixer; swap out to the whisk attachment.

Scrape down the sides of the bowl; add the cold whipping cream and beat on low until incorporated, about 30 seconds.

Beat on medium-high until soft peaks form.

Using a spoon, dollop a generous amount of whipped mascarpone into the bottom of your bowl or glass.

Add a layer of lemon curd.

Add another layer of mascarpone.

Add a generous crumbly amount of cooled oat cookie crumble, broken into small pieces.

Add another dollop of mascarpone.

Add a spoonful of blackberry jam and top with fresh blackberries!