Add dark chocolate to a double boiler and heat, stirring until melted. Alternatively, you can place dark chocolate in a medium-sized glass bowl and microwave in 30 second increments until smooth and melted, stirring every 30 seconds. Remove and let cool slightly.
Add avocado to a food processor or high-powered blender and puree until smooth. Alternatively, add the avocado to a large bowl and mash with a fork until somewhat smooth.
Once dark chocolate has cooled slightly, reserve 2-3 Tbsp. in a small bowl. Carefully add the rest to the food processor or bowl with the avocado. Blend or mix well, scraping down sides with a rubber spatula as needed to blend evenly.
Add vanilla extract and a pinch of sea salt to the mix.
Place in a bowl and refrigerate for at least 60 minutes (or freeze for 20-30 minutes) until somewhat firm.
Line a sheet pan with parchment paper and add cocoa powder to a small bowl.
Once mixture is chilled and somewhat firm, remove from the fridge or freezer. Using a small ice cream scoop or tablespoon, measure out 1” balls. Roll with hands until smooth. (Note: Your hands will get messy!)
Roll balls in cocoa powder one at a time until coated and place each on a parchment-lined sheet.
Once all balls have been formed, use a small spoon to drizzle the reserved melted chocolate over the balls evenly. If desired, top with a sprinkle of sea salt. Enjoy right away with sliced strawberries or place in fridge until ready to serve.