In a small saucepan, heat the milk over medium-high heat until bubbling at the edges. Remove it from the heat and add the tea leaves in the milk to steep. Cover for 10 minutes, strain the liquid through a fine sieve and set aside.
Preheat the oven to 350°F (175˚C). Grease a 9-inch (23-cm) round cake pan with butter. Line base and side with parchment paper.
Combine the chocolate and butter in a large metal bowl, set it over a saucepan of simmering water on low heat. Stir frequently until the chocolate and butter are melted and smooth. Let the mixture cool to room temperature.
Whisk in the infused milk, vanilla extract, and salt.
In a large mixing bowl beat the egg yolks and 1/4 cup of sugar with an electric mixture until thick and creamy. Fold the egg yolk mixture into the chocolate mixture.
Add in the ground almond flour.
In a separate mixing bowl, use an electric mixer set at medium-high speed to beat the egg whites until soft peaks form while adding in the remaining sugar a tablespoon at a time. Continue beating the whites until they form stiff, glossy peaks. Use a rubber spatula to gently fold the egg whites into chocolate mixture in two batches.
Pour the batter into the cake pan, spreading it evenly across the top with an offset spatula. Bake for 35-40 minutes, or until the cake’s center is slightly gooey and its edges pull away from the pan.
When the cake is finished baking, transfer it to a wire rack and let it cool for 15 minutes, turn cake, top side up onto a wire rack and let it cool to room temperature. Dust the top with cocoa powder.
To make the candied kumquats, in a small sauce pan bring water and sugar to a boil over medium-high heat until the sugar has dissolved. Add the kumquat slices, then reduce the heat to medium and simmer it until the kumquats are tender and translucent, about 15 minutes.
Serve each piece of cake with creme fraiche and a spoonful of candied kumquats.