For the dough: In a small bowl, combine the flour, sugar, orange zest, vanilla seeds, nutmeg and salt and whisk together. In a large mixing bowl, add the butter and egg yolks. Using an electric hand mixer on the lowest setting, begin mixing while slowly adding the dry ingredients until the mixture is combined. Shape the dough into a disc, wrap in plastic and put in the fridge for 1 hour.
For the semolina cream: Pass the ricotta through a fine mesh sieve into a 2-quart heatproof bowl. Stir in the sugar, lemon zest and salt.
Tie the sage and mint sprigs together with kitchen twine. In a medium pot, heat the milk with the herb bundle over medium heat to infuse the milk with the flavor. When the milk begins to lightly simmer, remove the herbs, then slowly sift the semolina flour into the pot. Cook over medium heat, gently stirring until thickened. Turn off the heat and whisk to eliminate lumps. Mix gently for a couple of minutes until fluffy and creamy.
Pour the semolina mixture into the heatproof bowl with the ricotta and mix well to combine.
Heat the oven to 350 degrees F. Butter a 9-inch removable bottom tart pan. On a flat, floured surface, roll out the dough and place in the pan, pressing it over the rim to remove the excess.
Pour the semolina mixture into the tart pan; flatten the mixture using a rubber spatula or a spoon and bake, about 45 minutes. Set aside to cool for at least 20 minutes.
For the chocolate cream: Set another heatproof bowl over a pan with simmering water and melt the chocolate. Remove from the heat, add the cream and whip it well for about 2 minutes. Pour over the top of the cooled tart and spread it out using a rubber spatula. Cool for 15 minutes before serving.