1. Heat milk and 1/4 cup heavy cream until almost boiling.
2. Using a hand whisk, beat egg yolks with sugar and cornstarch. While beating vigorously, pour milk and cream mixture into egg-yolk mixture. Mix well and pour the combined mixture back into the pot. Cook, stirring constantly, until thickened.
3. Remove from heat and add chocolate and praline paste. Add butter and mix well, until thoroughly combined. Cover mixture with plastic wrap, pressing down so that plastic wrap is touching the mixture’s surface as much as possible. Refrigerate for two hours.
4. Remove from fridge and beat for three minutes in mixer on medium speed. Whip up the remaining 1/4 cup heavy cream. Separate one third of the chocolate-nougat mixture and fold in whipped cream.