First, pre-heat the oven to 180 degrees. Next, cut the plums into small pieces. Add them to a bowl, together with the cinnamon & sugar. Mix & fill into a casserole dish & set aside.
Finally, place the butter (it shouldn't come straight from the fridge, yet not too warm either), oats, buckwheat flower, spieces & sugar in the bowl & mix well until it starts to crumble. I find, it works best, simply using my hands. If you think it's still to wet, simly add a little more buckwheat flour or some more oats. If it's too dry, add a tablespoon of butter.
Add the crumble to the casserole, top with some fine almond slices & place it in the middle part of your oven. Cook roughly 20-30 minutes, until the crumble becomes a little brown.
Once finished baking, top with some puffed quinoa or millet if you like. Serve with vegan whipped cream (such as coconut cream) or some custard. I can also recomment vanilla or cinnamon ice cream.