For Chocolate Hazelnut Tart: Combine flour, sugar, brown sugar, 2 teaspoons of salt, butter, coconut oil, and 2 eggs in the bowl of an electric mixer fitted with a paddle attachment. Mix on medium speed until combined.
Add water and mix on low speed for 1 minute. Increase speed and blend until dough is smooth. Do not overmix.
Divide dough into two even balls and wrap in plastic wrap. Rest in refrigerator for 45 minutes.