- Briefly pulse the flour and salt in the food processor until combined. Add the butter and pulse until the mixture resembles coarse cornmeal. Add the sour cream. Pulse until the dough starts to form a ball. Remove the dough and shape by hand into a disc. Cover with plastic wrap and refrigerate for 30 minutes.
- Roll out the dough to about 3 mm (1/8 inch) thick. With a 9-cm (3 1/2-inch) cookie cutter, cut 24 circles. Line the tartlet pans with the dough, making sure it extends all the way up the sides. Place the pans on a tray and refrigerate for 30 minutes.
- With the rack in the middle position, preheat the oven to 190°C (375°F).
- In a skillet over medium heat, soften the onion and garlic in the oil. Season with salt and pepper. Add the ham and continue cooking until lightly browned. Add the endives and remove from the heat. Adjust the seasoning. Set aside in a bowl and let cool.
- In a bowl, mix the eggs and milk. Season with salt and pepper.
- Divide the ham mixture and cheese among the tart shells. Pour in the egg mixture and garnish with chives. Bake until golden, 30 to 35 minutes.