Place almonds in a blender; grind into a flour. Transfer to a large bowl.

Place dates in the blender; blend until very smooth and creamy.

Mix blended dates with the almond flour in the bowl. Stir in cocoa powder. Spread mixture evenly into a shallow 9x11-inch dish, pressing firmly with the back of a spatula to make a flat crust.

Place cashews in the blender; process, scraping down the sides every 1 to 2 minutes, until very smooth and creamy, 8 to 10 minutes. Add agave nectar, baby spinach, and peppermint extract; blend until filling is smooth and uniform in color.

Spoon filling onto the crust and smooth the top with the back of a spoon.

Freeze until set, about 30 minutes. Cut into 35 squares.