Heat half-and-half in medium saucepan over medium heat until just simmering. Meanwhile, whisk yolks, sugar, and salt in medium bowl until smooth. Add flour to yolk mixture and whisk until incorporated. Remove half-and-half from heat and, whisking constantly, slowly add 1/4 cup to yolk mixture to temper. Whisking constantly, return tempered yolk mixture to half-and-half in saucepan.
Return saucepan to medium heat and cook, whisking constantly, until mixture thickens slightly, about 1 minute. Reduce heat to medium-low and continue to simmer, whisking constantly, 8 minutes.
Increase heat to medium and cook, whisking vigorously, until bubbles burst on surface, 1 to 2 minutes. Remove saucepan from heat; whisk in butter and vanilla until butter is melted and incorporated. Strain pastry cream through fine-mesh strainer set over medium bowl. Press lightly greased parchment paper directly on surface and refrigerate until set, at least 2 hours and up to 24 hours.
For the Cake:
Prepate baking pans. Grease and flour 2 6" rounds. You can place a parchment round on the bottom, if necessary
In a medium bowl, whisk together flour, Instant Clear Gel, cardamom, salt and baking powder. Set aside.
Preheat oven to 350° F.
In a small saucepan, heat the milk and butter just to a beginning boil. Remove from heat, stir to melt the butter, then cover with a lid. Drape a dishtowel over the pan to keep warm.
In a mixing bowl, beat the eggs and sugar on high speed for 3-4 minutes or until eggs are a light lemon-color and thick.
Add the oil and vanilla, beating on low just to combine.
Add flour mixture and beat on low until combined to a thick, smooth batter.
Gradually add the hot milk/butter mixture and beat on low to combine.
Pour evenly into prepared pans (I use a kitchen scale to even them out). Tap lightly to disperse just the biggest bubbles.
Bake at 350° F for 30 minutes, or until a toothpick comes out clean and the tops spring back to the touch. The cakes should be an even light golden brown.
Transfer cakes to wire rack and cool for 10 minutes, then tap out to cool completely on a wire rack.
For the Glaze:
Bring cream and corn syrup to simmer in small saucepan over medium heat. Remove from heat and add chocolate. Let the chocolate sit in the hot cream for 3-4 minutes, then stir until smooth.
To Assemble:
Place one cake round on large plate. Whisk pastry cream briefly, then spoon onto center of cake. Using offset spatula, spread evenly to cake edge. Place second layer on pastry cream, bottom side up, making sure layers line up properly. Press lightly on top of cake to level.
Pour slightly-cooled glaze onto center of cake. Use offset spatula to spread glaze to edge of cake, letting excess drip decoratively down sides. Chill finished cake 3 hours before slicing. Cake may be made up to 24 hours before serving.
Notes
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