Preheat your oven to 350°F/175°C.
Make granola by adding the rolled oats, ground cinnamon, ginger, allspice, cardamom, and salt to a large bowl. Pour in the maple syrup and 4 tablespoons of oil. Mix until well combined.
Transfer the mixture to a rimmed baking sheet lined with parchment paper and spread it into an even layer. Bake the granola for 12 minutes, stir, and bake it for another 10-12 minutes, checking after the 10-minute mark.
Let the granola cool completely. Once cooled, transfer it to the bowl of a food processor. Turn the machine on and let it ‘process’ the granola butter, scraping down the sides with a silicone spatula as needed.
Once it starts to clump together, add an additional 2-4 tablespoons of oil until it's reached your desired consistency. Two will give it a thicker texture whereas more oil will make it more spreadable and drippy.
Transfer the mixture to a tightly sealed glass jar. Store in a cool, dark place for up to 2 weeks or in the fridge for up to 1 month. It becomes very thick when cold. To soften either place in the microwave for a few seconds or put the jar in a bowl of warm water until it's easier to stir.
Makes 1 heaping cup (8 ounces).