put the poppy seeds in a small bowl. Pour the boiling water over them and stir to coat. Allow to sit for one hour, stirring halfway through.
preheat the oven to 350°. Grease 12 jars each 8 ounces a with butter. Whisk together the flour, cornstarch, and baking powder in a medium-size bowl and set aside. In a large bowl or in the stand mixer, beat the butter and sugar until creamy. In another bowl, lightly beat together the egg yolks and eggs. Alternate adding the flour and the eggs to the butter mixture, mixing after each addition. Stir in the almond extract, the vanilla extract, and the moistened poppy seeds.
fill each jar half full with batter and sprinkle with sliced almonds. Place the jars 2 inches apart on a large baking sheet and bake for 25 to 30 minutes, until the tops of the cakes spring back When tapped. Remove from the oven and allow to cool on the baking sheet. Serve warm or at room temperature. Makes 12 individual almond poppy seed cakes