In a food processor, blend hazelnuts, dates, cocoa powder, ground nuts, and nut butter until dense and sticky. Add milk gradually, pulsing just until the mixture holds together. Press firmly into the prepared pan in an even layer.

In a high-speed blender, blend cashews, coconut cream, condensed milk if using, almond butter, maple syrup, and vanilla until completely smooth. Pour over the base and smooth the surface. Freeze until fully set, at least 4 hours.

Lift the slab from the pan and cut into bars or cubes. Melt the chocolate with the coconut oil in a heatproof bowl set over gently simmering water or in short microwave bursts, stirring until smooth. Dip each piece into the chocolate or spoon chocolate over the top. Sprinkle with chopped hazelnuts if using. Return to the freezer until the coating is firm.

Let stand at room temperature for 10 minutes before serving for the best texture. Store frozen for up to 2 months.