To make the crust, in a food processor, pulse the graham crackers until fine crumbs. Add sugar, cocoa powder and melted butter and pulse until combined. Press the mixture evenly onto the bottom and slightly up the sides of an ungreased 9-inch spring form pan. Refrigerate while preparing the filling.
Preheat the oven to 350°F (175°C).
To make the filling, break the chocolate into small pieces and place in a medium heatproof bowl. Slowly melt the chocolate over simmering water, aka double boiler. Remove from heat and set aside to cool. If desired, reserve a small amount (about 3 tablespoons) of melted chocolate for drizzling.
In a large mixing bowl with paddle attachment, beat the cream cheese until fluffy on medium speed, about a minute. (Or you can also use electric hand mixer.) Add condensed milk and Greek yogurt, and continue to beat for about 2 minutes, or until smooth, scraping the sides of the bowl once. Stir in melted chocolate, vanilla extract and salt. Beat in the eggs one at a time and mix just until combined on low speed. (Don’t beat the mixture too long and too fast after you add the eggs. Otherwise too much air will incorporate to the batter, which might cause a crack in the cooked cheesecake.) Pour the batter into the prepared crust.
Bake for 50-60 minutes, or until the edges of the cheesecake is set, but the center is slightly wobbly. Cool on a wire rack for 5 minutes. Carefully run a knife around edge of the pan to loosen; cool for another hour. Then refrigerate for at least an hour to cool completely.
To make the frosting, place the pecans and coconut flakes in a medium bowl and set aside.
In a medium saucepan, whisk together egg yolk, brown sugar and salt until combined. Stir in butter. Then whisk in heavy cream and vanilla extract and cook over medium high heat for 5-7 minutes, whisking occasionally. The mixture will be thickened, but still runny. Pour it over the pecans and coconut flakes and mix until well combined. The mixture will be slightly runny. Cool to room temperature, then place it in a fridge to cool completely, until ready to use. At this point, the frosting will be thick and spreadable. Spread the frosting evenly on the cooled cheesecake. If reserved, re-melt the reserved chocolate and drizzle over the cheesecake. Store in the fridge, covered, for up to 3 days.
For step-by-step photos and additional notes, read the post above.