In a small pot over medium heat, whisk together the coconut milk and sugar. Cook for 20–25 minutes, until thickened and reduced by nearly half. Remove the pot from the heat and let cool completely, about 20 minutes.
Once cooled, transfer the coconut milk mixture to a high-speed blender and add the spinach and mint extract. Blend on high speed for 30–60 seconds, until the spinach is completely broken down and the mixture has a minty green hue.
Add the coconut cream to a chilled metal bowl. Using an electric hand mixer, beat the coconut cream on high speed for 3 minutes, until soft peaks form. Add the melted coconut oil and briefly whip to combine.
Add the spinach mixture to the whipped coconut cream mixture and beat on medium speed for 1 minute, until well combined and fluffy. Fold in the cacao nibs.
Distribute the mixture evenly between the prepared muffin cups. Top with more cacao nibs.
Freeze the cups for 30–60 minutes, until set but not too hard to bite through. Serve immediately, or keep in the freezer to let harden completely, then let sit at room temperature for 15–20 minutes to soften before serving.