Step 1 - Dehydrate the Pastry Architecture:

Preheat your oven to 320°F (160°C). Use a serrated knife to slice the stale croissants into 1-inch chunks. Spread the pieces evenly across a baking sheet in a single layer and toast for 8-10 minutes until the exterior surface is crisp and dry to touch. Remove and cool completely at room temperature. This removes water from the pastry cells so they can draw in the rich cream custard later.

Step 2 - Synthesize the Molten Core:

Combine the 4 ounces of chopped dark chocolate, 1/4 cup heavy cream, and 1 tablespoon of butter in a small saucepan over low heat. Stir continuously for 2-3 minutes until completely melted and glossy. Pour the ganache into 4 small silicone molds or onto parchment-lined tray creating 4 separate 2-inch diameter disks. Freeze for at least 15 minutes until completely solid and rock-hard.

Step 3 - Emulsify the Rich Custard Base:

In a large mixing bowl, whisk the 3 egg yolks, 1 whole egg, and granulated sugar together for 60 seconds until slightly pale. Slowly pour in the 1 cup of heavy cream, whole milk, vanilla bean paste, and sea salt while whisking continuously. Mix smoothly until completely uniform with no air pockets - the custard should be glossy and golden-yellow with visible vanilla specks.

Step 4 - Execute Capillary Soak and Layering:

Grease your four 8-ounce ramekins with butter. Place a few dry croissant pieces in the bottom of each dish creating a 1-inch deep base layer. Pour 2 tablespoons of custard over the bottom layer. Remove the frozen ganache cores from the freezer and place one disk directly in the center of each ramekin. Pack the remaining croissant pieces tightly around and on top of the chocolate core, filling to within 1/4 inch of the rim.

Step 5 - Flood and Rest the Matrix:

Divide the remaining custard evenly among the ramekins, pouring slowly over the top croissant pieces. Scatter the extra chocolate chunks into the surface spaces. Press down gently with your fingers to submerge all top layers beneath the custard surface. Let the assembled dishes rest undisturbed at room temperature for exactly 15 minutes to allow the dry pastry cells to draw the custard into their core spaces through capillary action.

Step 6 - Bake to Precision Equilibrium:

Increase oven temperature to 350°F (177°C). Place the filled ramekins onto a baking sheet and transfer to the oven. Bake for 22-25 minutes until the tops are deeply golden-brown and puffed, but the center jiggles slightly when shaken. The tops should be caramelized with crispy edges. Remove from the oven, cool for 5 minutes on the baking sheet, and serve immediately to maintain the hot, liquid state of the chocolate lava center.