Arrange oven racks so one is in top third and one in bottom third of oven. Preheat oven to 325°F (160°C). Line two baking sheets with parchment paper. Trace two 8-inch (20 cm) circles on each piece of parchment paper. Flip paper over.
Sift together ground almonds, icing sugar and flour. In bowl of stand mixer fitted with whisk attachment, beat egg whites on medium speed until frothy. Gradually add granulated sugar while whisking. Increase speed to high; continue to whisk until whites hold medium-firm peaks. Remove bowl from mixer. Gently fold in half of almond mixture until almost combined. Gently fold in remaining almond mixture, being careful not to overmix. Transfer mixture to a piping bag fitted with medium-sized plain round tip (alternatively, transfer to zippered plastic bag and cut off one corner). Pipe mixture in a spiral from the outside to the inside of each of the four traced circles. Even out and fill in any gaps using the back of a spoon. Bake for 15 to 20 minutes, switching baking sheets top to bottom halfway, or until lightly golden. Cool on baking sheets to room temperature.
Place green tea bags in one small bowl, Earl Grey tea bags in another small bowl, and vanilla seeds and cardamom in a third small bowl. Add ¼ cup (50 mL) freshly boiled water to each of the tea bag containing bowls; steep for 10 minutes. Strain separately, pressing on bags well to squeeze out all moisture. Add 2 tbsp (25 mL) freshly boiled water to the vanilla mixture. Set all three infusions aside to cool.
Line 9 inch (2.5 L) springform pan with plastic wrap, making sure to press into the corner well. Set aside.
In stand mixer fitted with whisk attachment, combine ¾ cup (175 mL) of the icing sugar with macha powder (if using). Add 2 tbsp (25 mL) of the steeped green tea infusion, 1 cup (250 mL) of the whipping cream, and food colouring (if using). Beat until medium peaks form; do not overmix. Using rubber spatula, scrape into prepared springform pan; tap on the counter to level, then smooth with back of a spoon.
Flip almond meringue cakes over so parchment paper is up. Gently peel parchment paper off. Place one cake on top of green tea ice cream in springform pan.
In same bowl, beat ¾ cup (175 mL) of the icing sugar, all of vanilla infusion and 1 cup (250 mL) of the whipping cream until medium peaks form; do not overmix. Using rubber spatula, scrape into springform pan; tap on the counter to level, then smooth with back of a spoon. Top with another almond meringue cake.
In same bowl, beat remaining icing sugar, 2 tbsp (25 mL) of Earl Grey infusion and remaining whipping cream until medium peaks form; do not overmix. Using rubber spatula, scrape into springform pan; tap on the counter to level, then smooth with back of a spoon. Place remaining two almond meringue cakes back to back and place on top of Earl Grey layer. Cover with plastic wrap. Freeze until fully hardened, preferably overnight.
Choose a saucepan that the bowl of a stand mixture will sit on top of. Bring water in saucepan to a simmer. In stand mixer bowl set over (not in) simmering (not boiling) water, whisk egg whites with sugar constantly until sugar dissolves and mixture is frothy, about 3 to 5 minutes. It will be quite warm to the touch. Transfer bowl to stand mixer; surging whisk attachment, beat until mixture is almost doubled in volume and is room temperature, about 10 minutes. Beat in vanilla.
Remove hardened cake from freezer. Release clip and remove side of pan. Invert onto cake plate; remove springform base and plastic wrap. Quickly spread about one-half of marshmallow topping around side of cake only. Return cake to freezer. Set remaining marshmallow topping aside.
Cut two strips of parchment paper measuring 38 X 8 cm; place on baking sheet. Heat white chocolate chips in microwave on HIGH for 1 to 1-1/2 minutes, stirring once or twice, until melted. Stir in ¼ tsp (1 mL) canola oil. Using a spoon, drizzle white chocolate in swirly pattern over the parchment paper strips. Set aside to cool.
Heat semi-sweet chocolate chips in microwave on HIGH for 1-1/2 to 2 minutes, stirring once or twice, until melted. Stir in 1 tsp (5 mL) canola oil. Pour half down centre of each strip of parchment; gently spread evenly to the edges. Remove cake from freezer. Quickly wrap parchment strips around the side of cake with the chocolate facing inwards, starting one where the first one ends to completely surround the side of the cake. Return cake to the freezer to harden collar, about 15 minutes.
Remove cake from freezer. Gently peel off parchment paper. Dollop remaining marshmallow topping over top of cake. Spread with back of spoon to cover top. If desired, gently brown with a torch. Return cake to freezer until ready to serve.
Let stand at room temperature for 10 minutes before cutting. Cut using hot dry knife, running knife under hot water and wiping dry between cuts.
