While churning, prepare your raw brownie by processing dates in the food processor until small bits remain - it will likely form into a ball. Remove and set aside.
Add mixture to your chilled ice cream maker bowl and churn according to manufacturer’s instructions until thoroughly chilled, about 45 minutes. It should resemble thick soft serve (see photo).
Add remaining ingredients, including DRAINED cashews and remaining 1/4 cup fresh mint (vanilla extract is optional) and blend until creamy and smooth - about 3-4 minutes, using the "liquify option" if you have it. Taste and adjust sweetness/minty-ness as needed.
OPTIONAL STEP: When ready to prepare ice cream, steep HALF of your fresh mint leaves in the coconut milk. Bring the coconut milk to a simmer in a small saucepan and add the mint leaves, then turn to low. Use a wooden spoon or muddler to puncture the mint so it infuses the coconut milk. Keep on low for 15 minutes, then kill heat and let cool. Once cooled, strain out the mint leaves using a fine mesh strainer and pour the coconut milk right into a blender. (If not doing this step, just add all of the fresh mint and coconut milk right into the blender. The flavor won't be AS strong, but it will still be delicious.)
Set your churning bowl in the freezer the night before to chill. Soak your cashews the night before as well, or for at least 4-6 hours before blending.