Molasses Gingerbread Cake with Vanilla Custard

Steps

1. Make the custard first so it can chill. In a saucepan, whisk the granulated sugar, cornstarch and one quarter of the salt, then whisk in one of the eggs (one third of the egg total) until smooth.
2. Gradually whisk in the whole milk. Cook over medium heat, whisking constantly, until it bubbles and thickens and reaches at least 160°F (71°C), then whisk 1 minute more.
3. Off the heat, whisk in the butter and the vanilla. Scrape into a bowl, press plastic wrap onto the surface and refrigerate at least 2 hours until cold and set.
4. Meanwhile, heat the oven to 350°F (175°C). Lightly oil a 9-inch square pan with a little of the canola oil and line the bottom with parchment.
5. In a medium bowl, whisk the flour, baking soda, ground ginger, cinnamon, cloves, nutmeg and the remaining three quarters of the salt.
6. In a large bowl, whisk the molasses, brown sugar, remaining canola oil, the remaining two eggs and the grated fresh ginger until glossy, then whisk in the buttermilk.
7. Add the flour mixture to the molasses mixture and stir just until no dry streaks remain. Pour the batter into the pan and smooth the top.
8. Bake 35 to 40 minutes, until a toothpick inserted in the center comes out clean. Cool 10 minutes in the pan, then turn out onto a rack and cool completely, about 1 hour.
9. With a long serrated knife, split the cooled cake horizontally into two layers. Whisk the chilled custard until smooth and spread it over the bottom layer, leaving a small border.
10. Set the top layer on the custard, chill 30 minutes to firm, then cut into 12 slices. Keep leftovers refrigerated.