Sift the cocoa powder, cornstarch and salt into a medium bowl. Slowly mix in the cream, eliminating any visible lumps; the mixture will be thick. Mix in the egg yolks until combined. Set aside.
Heat the Bonne Maman Cherry Preserves, spoon out the cherries and set aside, reserving liquid.
Heat the milk and sugar in a 2-quart saucepan over medium heat, stirring often until the sugar dissolves. When bubbles form around edge of milk, remove pan from heat.
Whisk about half of the hot milk into the cocoa mixture. When smooth, whisk mixture back into milk remaining in the saucepan.
Bring pudding to a boil over medium-high heat, whisking slowly and scraping bottom of the pot to prevent scorching. When the pudding thickens, and large bubbles roll up to the surface with small fast bubbles on the edges, turn down heat down to medium and whisk vigorously for 2 minutes.
Remove pan from heat, and whisk in vanilla and liquid from cherry preserves.
Place a chocolate wafer cookie (or multiple if using a larger serving dish) in the bottom of each dish and spread cherry preserves on top. Fill to the top with pudding, and chill for an hour or up to three days in refrigerator, covered with plastic wrap.
Decorate with a dollop of whipped cream and reserved cherries before serving.