Line a baking tray with wax paper, and carefully dole out 1 teaspoon of chocolate hazelnut spread 2 inches apart from one another. Freeze until solid, about 2 - 3 hours, preferably overnight.

Preheat the oven to 350 (F) and line a muffin tin with cupcake cases.

Whisk together 1 large egg, 1/4 teaspoon vanilla and the remaining milk together in a liquid measuring cup, before pouring into the flour mixture and continuing to beat until just incorporated. Scrape down any unmixed ingredients from the side of the bowl and the paddle, before continuing to mix for another minute until the batter is just smooth. Be careful not to overmix!

When the cupcakes are cold, frost each cupcake with generous amounts of chocolate hazelnut ganache frosting, topping each with a Ferrero Rocher bonbon.

Combine 10 ounces bittersweet chocolate and 2/3 cup confectioner's sugar in a medium, heatproof bowl.

In a small saucepan over medium heat, bring 3/4 cup plus 1 tablespoon heavy cream to a gentle simmer, whisking occasionally. Pour the hot cream into the medium, heatproof bowl containing the chocolate and confectioner's sugar mixture. Stir the mixture with a heatproof, rubber spatula until the sugar is dissolved.

Once the sugar has dissolved, nestle the medium, heatproof bowl over a medium saucepan of simmer water to make a double boiler — be sure that the water in the saucepan doesn't touch the bottom of your heatproof bowl. Gently cook, stirring with a rubber spatula, until all the chocolate is melted and the mixture is smooth. Remove the bowl from the heat.

In a separate, smaller heatproof bowl, whisk together 2 large egg yolks. Pour about 1/2 cup of some of the melted chocolate mixture into the yolks while whisking, to temper them. Pour the tempered mixture back into the larger, heatproof bowl containing the rest of the original mixture and whisk to combine. Add 3 tablespoons unsalted butter and whisk until smooth and completely dissolved into the mixture. Add another 1/3 cup chocolate hazelnut spread and whisk until smooth and fully incorporated.

Allow the ganache to cool for about 15 to 20 minutes, before using immediately. It’s important that you let the ganache cool before using, or it will be too liquidy and hard to work with. The ganache will thicken as it cools.