Spray an 8 1⁄2-by-4 1⁄2-by 2 3⁄4-inch loaf pan with nonstick spray. Line the sprayed pan with plastic wrap, allowing a 1 1⁄2-inch overhang on all sides.

In a stainless-steel bowl, combine the chocolate, butter, and peanut butter. Place the bowl over a pan of simmering water, making sure the bottom of the bowl does not touch the water. Heat, stirring occasionally, until the chocolate and butter melt. Remove from the heat and whisk until smooth.

Combine the egg yolks and sugar in the bowl of a stand mixer fitted with the whip attachment and whip on high speed until thick, about 1 minute. Remove the bowl from the mixer stand. Using a wooden spoon, stir in the chocolate mixture in 3 equal additions. The mixture will be quite thick.

In a separate bowl, whisk the cream until it starts to thicken. Using a spatula, fold the cream into the chocolate mixture in 4 equal additions. Spread the batter in the prepared pan. Cover with the plastic wrap overhanging the sides and refrigerate until firm, at least 4 hours.

To unmold the terrine, fold back the plastic wrap and invert the pan onto a wire rack. Pull on a corner of the plastic wrap to release the terrine from the pan. Lift off the pan and carefully remove the plastic wrap. Line a baking sheet with parchment paper and place the rack on it. Return the terrine to the refrigerator while you make the glaze.

To make the glaze, in a stainless-steel bowl, combine the chocolate, butter and corn syrup. Place the bowl over a pan of simmering water, making sure the bottom of the bowl does not touch the water, and heat, stirring occasionally, until the chocolate and butter melt. Remove from over the heat and whisk until smooth. The glaze should be pourable but not so thin that it will run off the terrine. If the glaze is too thin, let it sit at room temperature for about 30 minutes.

Slowly pour the glaze evenly over the top of the terrine, allowing it to stream evenly down the sides. With an offset spatula, spread the glaze to cover the terrine smoothly and completely. Refrigerate until the glaze is set, about 30 minutes.

To make the sugared peanuts, preheat the oven to 350 F. In a bowl, whisk the egg white until frothy. Whisk in the sugar. Add the peanuts and mix until they are evenly coated with the mixture. Spread the peanuts in a single layer on a rimmed baking sheet and place in the oven. Toast the nuts, stirring them every 5 minutes, until dry and golden brown, 15 to 20 minutes.

To serve, transfer the terrine to a serving platter and arrange the sugared peanuts on top. Cut the terrine with a hot, dry knife.