In a food processor, combine the almonds and hazelnuts. Grind the nuts to a very fine consistency. Add the sugar, cacao powder, and salt and pulse the ingredients. Pour the mixture into a large bowl. Add the oil and vanilla and toss, adding water until the mixture sticks together.
Press the mixture into a 12" x 12" baking dish and bake for 10 minutes, or until brown. Let cool before pouring the filling on top.
To make the filling
Place the tofu, water, vanilla, mint, sugar, and salt into a medium saucepan. Mash the tofu lightly into smaller pieces with a potato masher or whisk. Bring the mixture to a boil. Reduce the heat and let simmer for 15 to 20 minutes, or until the liquid reduces and the tofu turns light brown. Turn off the heat, add the chocolate chips, and stir until melted.
Place the mixture in a high-speed blender and blend until smooth. Pour into the cooled crust. Refrigerate for at least 2 hours, or until well chilled. Slice and serve cold.
Any remaining filling can be refrigerated. It will stiffen when cool, but can be melted down over low heat or in a double boiler and poured into a pre-baked tart shell.