Line 2 baking trays with non-stick baking paper.
Preheat your oven to 180 Degrees C (360 F).
Add almond flour and caster sugar to a medium-size bowl, and stir to combine.
In a small bowl or cup, dissolve the coffee powder in the boiling water and set it aside to cool.
Lightly whisk the egg whites until they are frothy.
Add the cooled coffee, whisked egg whites and vanilla extract to the almond flour and caster sugar. Stir well until the ingredients are thoroughly combined.
Using a teaspoon, roll into small balls about 3 cm (1 ¼ inch) in diameter. Alternatively, to obtain even size balls, you can use a small ice cream scoop.
Toss the balls in the flaked almonds, and place them on the prepared trays, leaving a small amount of room between the balls for the heat to circulate.
Press down gently with your fingertips to slightly flatten the cookies.
Bake for about 12-15 minutes until lightly browned. (See Note 4) Remove from the oven and place on cooling racks.