• Preheat oven to 375°F. Place 12 muffin liners into a standard muffin pan and set aside.

Make the crust.

• Add graham crackers and brown sugar to the bowl of a food processor. Pulse until there are fine crumbs with no large chunks remaining.
• Add melted butter and blend until combined and the crumbs begin to stick together.
• Divide the crust among the 12 muffin liners (about 1 Tablespoon of crust per liner) and press the crumbs into a solid crust using the back of a spoon. 
• Bake the crusts for 5 minutes, then remove the pan from the oven and turn the oven down to 325°F. Let the crusts cool while you prepare the cheesecake.

Make the cheesecake.

• Place the mini eggs into a plastic food storage bag. Seal the bag and place it on a hard, durable surface (like a cutting board). Use a rolling pin to smash the candies. Set aside.
• In a large bowl, add cream cheese, sugar, sour cream, heavy cream, vanilla, and salt. Using an electric handheld mixer, beat well on medium speed until smooth.
• Add egg and yolk and beat on low speed just until combined.
• Fold crushed mini eggs into the cheesecake batter.
• Spoon cheesecake onto the crusts so that muffin liners are nearly filled. (You'll use about 3 Tablespoons of cheesecake per liner.)
• Return the pan to the 325°F oven and bake for 15 minutes or until the edges of each cheesecake are set but the centers still wobble slightly when you jiggle the pan. Turn off the oven and let the cheesecakes sit in the warm oven with the door closed for 10 minutes. Then crack the oven door open and let the cheesecakes sit for another 10 minutes. Next transfer the pan to a wire rack and allow the cheesecakes to cool completely (about 1 hour). Finally, transfer the pan to the fridge and chill the cheesecakes for at least 2 hours and up to overnight.

Decorate the cheesecakes.

• While the cheesecakes are chilling, make the chocolate shavings using 1 ½ ounces of the chocolate baking bar. Using one square of the bar at a time, warm the chocolate lightly in the microwave for just 10 seconds on 50% power. Use a vegetable peeler repeatedly along the edge of the chocolate square to create chocolate shavings. Repeat with the other squares. Set shavings aside.
• Once the cheesecakes have chilled and set, make the ganache. Chop the remaining 2 ounces of chocolate baking bar and place into a small glass bowl. Heat the heavy cream in the microwave or on the stove just until simmering. Pour the heated cream over the chocolate and let it sit for 2 minutes. Then stir until the chocolate is completely melted and the mixture is smooth and shiny. 
• Spoon 1 teaspoon of chocolate ganache onto each cheesecake, using the back of the spoon to spread the ganache towards the edges of the cheesecake.
• Carefully sprinkle chocolate shavings around the edges of the ganache on each cheesecake, leaving space in the center of the circle.
• Add 3 Cadbury mini eggs into the center of each chocolate "nest" atop each cheesecake.
• Serve immediately or refrigerate. If refrigerating before serving, let cheesecakes sit at room temperature for 5 to 10 minutes immediately before serving.