Start by chopping the unsweetened baking chocolate into small pieces. Place these in a microwave-safe bowl and heat in the microwave for 30-50 seconds, stirring every 15 seconds until melted and smooth. Once melted, set aside to cool slightly.

In a stand mixer, cream 1/2 cup of softened salted butter and 3/4 cup of granulated sugar on high speed for 10-12 minutes until pale and fluffy. Scrape sides occasionally.

Slowly drizzle in the melted chocolate while mixing on low speed. Mix for another 5-7 minutes until fully incorporated and glossy.

Add whole eggs one at a time, mixing until each is fully blended. Beat on medium speed for 3-4 minutes after the last egg.

With mixer on low, add 1 teaspoon of vanilla extract, 1 teaspoon of cinnamon, and a pinch of cayenne. Mix until combined and adjust to taste.

Pour the chocolate filling into prepared crust and smooth the top with a spatula. Cover with plastic wrap and refrigerate for 3-4 hours until set.

Before serving, drizzle with chocolate ganache and serve chilled, optionally topped with whipped cream or chocolate shavings.