Cut the radicchio in half lengthways, place cut-down on a cutting board and slice up. Warm the oil in a pan and add the sliced radicchio. Sauté on medium-high heat for 3 minutes, until wilted. Stir in a sprinkle of salt and remove from the heat.
Press a shortcrust pastry shell onto a tart pan and spread the cooked radicchio all over the crust. Coarsely chop the walnuts and sprinkle over shortcrust pastry. Top with crumbled blue cheese evenly distributed.
Crack the eggs in a bowl and lightly whisk with a fork. Add the salt and milk and whisk until homogeneous. Pour egg mixture into the shortcrust case all over the other ingredients, reaching out to the sides of the tart.
Bake in the preheated oven at 180°C (350°F) for 40-45 min, moving the tart to the top part of the oven for the last 10 min to get a little more colour if necessary. Take it out of the oven and let set for 10 minutes before serving.
Notes
Please notice that the nutritional information provided is made by an online calculator and only meant to be used as a guideline.This quiche is rather thin, but quite flavourful. A whole tart feeds 3-4 as main, along with a light side dish like a salad. You can also cut it into 12 thin slices and serve it cold as appetizer, it makes for great finger food.