Prepare Creamy Latte Layer: In a saucepan, combine water, Olper’s milk powder, instant coffee, cornflour, and sugar. Whisk well. Cook on low flame, stirring continuously, until thickened (about 10-12 minutes). Let it cool while stirring occasionally, then cover and set aside.
Whip Cream: Place ice cubes in a large bowl and set another bowl on top. Add chilled Olper’s cream to the top bowl and beat until stiff peaks form.
Combine Coffee Sauce and Cream: Add the prepared coffee sauce to the whipped cream and mix until well combined. Transfer the mixture to a piping bag.
Prepare Chocolate Ganache: In a jug, combine chopped dark chocolate and Olper’s cream. Microwave for 2 minutes, stirring every 30 seconds until smooth. Set aside.
Prepare Coffee Dipping Mixture: In a jar, mix water, instant coffee, vanilla essence, and powdered sugar until dissolved.
Assemble the Cake: Dip whole wheat biscuits in the coffee mixture and layer them in a serving dish. Add a layer of the creamy latte mixture. Repeat with another layer of dipped biscuits and creamy latte mixture. Spread the chocolate ganache evenly on top.
Chill and Serve: Refrigerate the assembled cake for 2-3 hours or overnight. Serve chilled.