1. To get the ricotta started, combine the whole milk and buttermilk in a pot and bring to medium-high heat.
2. On a separate burner, pour the heavy cream into a small sauce pot and bring to high heat. Add the chocolate chips to a bowl on the counter. When the cream starts to boil, pour over the chocolate, about a half cup at a time, whisking continuously. Be careful not to add more cream until each pour has been combined with the chocolate.
3. Once the chocolate has melted completely and reached a saucy consistency, set aside to let cool.
4. Next, return to the whole milk-buttermilk combination. Stir to make sure nothing is burning on the bottom. **Be careful not to stir too aggressively, however, so that the curds can come together. When the solids start forming and pulling away from the sides of the pot, use a slotted spoon to remove them and transfer to a separate bowl. It is okay if ricotta does not drain completely. Season with salt and set aside.
5. Now, set your oven to broil. Thinly slice your baguette at a 45-degree bias to yield approximately 25 pieces. Place the bread onto a cookie sheet in a single layer and pop them into the oven to toast on one side. **Do NOT take your attention away from the oven because it will happen quickly.**
6. Finally, assemble the crostini: smear the toast with the homemade ricotta, add a spoonful of marmalade on top, and drizzle the dark chocolate ganache on top of the whole platter.