Whisk together all the ingredients for the ice cream in a bowl. If the cashew butter or tahini have clumps, melt them before using.
Once a smooth mixture has formed, pour the mixture into a shallow, airtight container.
Place in the freezer, with the lid on. Stir it every hour, until it reaches the desired texture. This will take around 5-6 hours.
In the meantime, use a fork to mix together the crumble ingredients. Set it aside at room temperature, covered, until ready to use.
For the roasted strawberries, whisk together the xylitol, hot water and cornstarch in a small bowl. Add this, along with the strawberries, into a skillet over medium-low heat.
Use a fork to lightly mash the strawberries as they heat up, until they are softened and mixed with the other ingredients. Continue stirring until the mixture has thickened, which will take a couple minutes. Then remove from the heat and set aside, partially covered, to cool down at room temperature.
Once the ice cream has achieved the desired texture, remove from the freezer.
Gently fold in the strawberry crumble. Serve right away, or place in the freezer and thaw to the desired consistency before serving.