- With the rack in the middle position, preheat the oven to 180 °C (350 °F). Butter and line a 20-cm (8-inch) springform pan with parchment paper.
- In a bowl, combine flour and baking powder.
- In another bowl, beat egg yolks, egg and sugar with an electric mixer until mixture forms a ribbon, about 10 minutes. Drizzle in oil. With a spatula, gently fold in dry ingredients. Pour into prepared pan. Bake for about 20 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool.
- In a small bowl, combine condensed milk and butter. Set aside.
- In a large bowl, sprinkle gelatine over water. Let bloom for 5 minutes. Add egg whites, beat lightly and set aside.
- In a small saucepan, bring sugar and water to a boil. Cook until a candy thermometer reads 115 °C (240 °F). Gently pour in gelatine mixture while beating constantly with an electric mixer. Beat for 6 to 8 minutes or until marshmallow is just warm and forms semi-firm peaks. With a spatula, gently fold in condensed milk mixture. Pour over cake. Let set for 2 hours in the refrigerator.
- In a saucepan, combine all ingredients with a whisk and bring to a boil. Simmer over low heat for 1 minute, whisking constantly. Remove from heat and let cool for 5 minutes.
- Unmould cake. Quickly spread glaze over the entire surface of the cake, letting it fall a little over the edges. Refrigerate for about 30 minutes. Cut with a knife, preferably warmed under hot running water.