In a small bowl, combine the cinnamon, ginger, cloves and nutmeg. Measure 3 tsp of gingerbread spice mix and add to the hot cream, dissolving completely. Add the cream and salt to the melted dark chocolate and stir until fully combined. Place in the fridge until chilled and thickened, 1-2 hours.
Beat the ganache with an electric mixer until it lightens in colour and thickens to piping consistency. Place in a piping bag fitted with a large, round tip.
Pour some melted milk chocolate into a chocolate mold of your choice and spread onto the inside of the mold to cover all walls. Place in the freezer to stiffen, about 5-10 minutes. Fill the chocolates with the ganache filling, then top with more melted chocolate. Return to the freezer to stiffen, 10-20 minutes.
Unmold, then wrap in aluminum foil. Place 1 chocolate in each house and tape the roofs shut. These chocolates are best stored in the fridge, unless you are tempering the chocolate, as tempered chocolate is best kept at room temperature.