Position rack in centre of oven, then preheat to 250F. Draw a 10-in. circle on a piece of parchment, then flip it over onto a large baking sheet.
Pavlova: Stir sugar with cornstarch in a small bowl. Beat egg whites with cream of tartar in a large bowl, with an electric mixer on medium, until foamy, about 1 min.
Gradually beat in sugar mixture, 1 tbsp at a time, until stiff and glossy peaks form when beaters are lifted, 4 to 6 min. Beat in almond extract.
Dollop 10 to 12 mounds of meringue onto parchment in a wreath shape using the circle outline as a guide. Create an indent in the centre of each dollop with the back of a spoon.
Bake for 40 min, then turn off oven. Leave pavlova inside oven for 4 hrs, then transfer to a rack to cool completely, about 1 hr.
Gently slide an offset spatula under pavlova to loosen it from parchment, then carefully slide it onto serving platter.
Topping: Beat cream with 2 tbsp icing sugar and amaretto in a large bowl, using an electric mixer on medium, until fluffy, 2 min.
Scoop over cooled wreath. Sprinkle with almonds, then top with raspberries and mint. Sift remaining 1 tbsp icing sugar over wreath.