Puree 1 cup of the blueberries and run through a fine mesh strainer. Set aside.
Make the pound cake according to recipe instructions but omit the orange oil and add in the lavender oil and blueberry puree instead. Make sure to use a very large loaf pan to bake the cake in. Let cake cool, removing from the baking pan after it's cooled for 10 minutes,
Place the mascarpone and powdered sugar in a bowl and beat together until smooth and creamy. Add the heavy cream and beat with an electric mixer until the mixture is thick and creamy(this will take a few minutes.) Beat in the lemon juice until just combined.
Spread the lemon mascarpone cream on top of the cooled cake. Top cream with the remaining blueberries and blackberries. Place sprigs of lavender on top, if desired.
Recipe by The Kitchen McCabe at https://www.thekitchenmccabe.com/2015/05/11/blueberry-lavender-pound-cake-with-lemon-mascarpone-cream/