Instructions

Preheat oven to 375°F.

Using your finger, very lightly smear the insides of each souffle ramekin with oil. Lightly dust with granulated sugar and set them on a baking sheet.

Weigh the berries while they're still frozen. Place them in a saucepan and stir in the cornstarch, lemon juice and a few tablespoons of sugar. Bring the ingredients to a simmer, stirring regularly until all the cornstarch and sugar dissolves (about 5 minutes).

Press the puree through a mesh sieve, stirring until you have nothing left but seeds. Pop the strained puree into the fridge to chill.

Separate the eggs into two bowls: whites in one and yolks in another. Whip the yolks with all but 1 or 2 tablespoons of the sugar until the yolks are thick and ribbony. Add the chilled raspberry puree and combine.

Whip the whites with the cream of tartar and when stiff, add the last couple tablespoons of sugar. Keep whipping until they form firm, glossy peaks.

Add ⅓ of the whipped egg whites —the sacrifice!— to the yolk and puree mixture and combine to lighten. Add the remaining whipped whites, carefully folding to preserve as much air as possible. The loftier, the better.

Gently spoon the soufflé mixture into each prepared ramekin. Fill to the top, smoothing with a knife.

Bake until they rise beautifully, and just begin to crack on too. Resist the temptation to open the oven door ( at least for the first 10 minutes of cooking) so they can take full advantage of the hot oven. Total cooking time will be about  15 to 20 minutes.

Remove from the oven, dust with powdered sugar and serve right away, as if anyone could stand waiting for these beauties!