In a medium-sized mixing bowl, combine the all-purpose flour, cocoa powder and sugar.
Drizzle the oil over the dry ingredients.
Using a fork or your fingers, mix the ingredients together until they form a crumbly texture. The streusel should have small clumps with a rich cocoa color.
If the streusel seems too dry and doesn't hold together, add a bit more olive oil, a half-teaspoon at a time, until you achieve the desired crumbly consistency.
On the other hand, if the streusel appears too wet and sticky, you can add a little more flour, a tablespoon at a time, until you get the right texture.
Once the streusel has the perfect crumbly texture, it's ready to use.
Sprinkle the cocoa streusel generously over muffins, coffee cakes, brownies, or any other baked goods of your choice before baking.