Place a rack in the middle of the oven and preheat to 200 °C / 390 °F or 190 °C / 375 °F (fan-assisted oven).
Add flour, oats, sugar, and cubed cold butter to a small bowl. Season with a pinch of salt and diced rosemary. Knead into a smooth dough, then place in the freezer for 5 minutes or in the fridge for 15 minutes.
Clean the peaches, remove the kernel and cut each peach into eight wedges. Add to a saucepan along with sugar, vanilla, and water. Set over medium heat, stir to combine, and cook for 15 - 20 minutes or until the peaches become tender. Dissolve the Agartina in a small bowl with two tablespoons of water or use gelatine. Soak 1/2 tsp gelatine in 1 tbsp water. Add the lemon juice and Agartina/gelatine to the peach mixture, stir to combine, then bring to a boil and simmer for 2 minutes. Add the blackberries and cook for another 2 minutes. Remove from the heat and bring to room temperature.
bake the crumble
Line a small baking dish with parchment paper. Take the dough from the fridge or freezer and grate it onto the prepared baking sheet. Use the large holes on your grater. Spread the crumble in a single layer and place it in the preheated oven. Bake for 15 minutes at 200 °C / 390 °F or 190 °C / 375 °F (fan-assisted oven).
Whip together whipping cream, sugar, and vanilla in a bowl until stiff peaks form. Stir in the greek yogurt and set aside until needed.
Divide all the components between four glasses. Fill them up in this order: yogurt cream, crumble, fruit topping, yogurt cream, fruit topping, and crumble. Serve as soon as possible.