Brush 6 holes of a deep muffin tin with a little sunflower oil and line the bases with rounds of greaseproof paper. Whisk the egg whites in a clean, dry bowl until stiff, moist peaks form. Whisk in the granulated sugar, a teaspoonful at a time, until it has all been added. Keep whisking for 1–2 minutes until thick and glossy.
Fold in the ground almonds and cream of tartar, then spoon the mixture into the prepared sections of the muffin tin. Sprinkle the flaked almonds over the top of each one. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 10–12 minutes until golden brown and set. Carefully loosen the edges of the cakes with a knife, then lift on to a wire rack to cool.
Put the fromage frais in a bowl and stir through the honey or icing sugar to sweeten, if liked. Swirl the thawed berry fruits through the fromage frais. Arrange the angel cakes on a serving plate, dusted with the icing sugar, if liked. Serve with the swirled fruits and fromage frais for spooning over.