Fill a large bowl with ice and ice water.
Bring 1 cup half and half, the almond paste, sugar, salt and cornstarch to a bubble over medium heat in a saucepan.
In a bowl, whisk together the remaining 1/4 cup half and half with the eggs. Slowly whisk in a few tablespoons of the bubbling mixture to temper the eggs, stirring constantly. Add the egg mixture back in the saucepan. Bring the mixture to a boil over medium heat, whisking constantly. Cool, stirring often, until the mixture coats the back of a spoon, about 3 to 4 minutes. Remove the pot and immedaitely place it in an ice bath, stirring continuously. Stir in the butter until it melts. Let the mixture cool completely.
Use a whisk of electric mixer, beat the heavy cream until peaks form. Gently fold it into the cooled almond cream. Place in the fridge until ready to use.