Preheat oven to 400 degrees.
Line a large baking sheet with parchment paper.
Trace a 9-inch circle on the parchment paper, using a plate as a guide. Flip the parchment paper over.
Spray it lightly with non-stick cooking spray.
In a large mixing bowl fitted with a whisk attachment, beat the egg whites and cream of tartar on medium speed until the egg whites are foamy, about 2 minutes.
Gradually add the sugar, a few tablespoons at a time.
Beat on high until stiff peaks form, and the egg whites are glossy and white, about 5 minutes.
Beat in vanilla extract.
Beat in cocoa powder and instant coffee granules.
Pile the meringue mixture onto the baking sheet in a round mound, using the traced circle as a guide.
Place in the oven and *immediately* turn the temperature down to 250 degrees.
Bake for 90 minutes, then turn off the oven, keeping the oven door closed. Do not open the oven door, or remove the pavlova. Allow it to cool in the oven for about 1 hour.
Remove pavlova from oven, cool completely on the pan.
Carefully shift the pavlova from the parchment paper to a cake plate or serving platter.