Preheat oven to 300ºF. In a bowl combine, 1/4 C honey, red pepper flakes, turmeric, a large pinch of salt, and 1 tsp water to create a thick paste. Add walnuts to the honey paste and stir to coat. Spread on a parchment-lined baking sheet. Roast for 15-20 minutes until nuts are crunchy and toasted. Remove from oven and set aside to cool.
While the walnuts are cooking, place the lentils and bay leaves in a medium saucepan. Cover with water and bring to a gentle boil. Simmer for 20 minutes or until tender. In a small bowl, combine vinegar, 1/4 C olive oil, remaining honey, 1/2 tsp salt, and pepper. Whisk until honey is incorporated. Drain the lentils and stir them into the mixture while they are still hot. Pour remaining oil into a small frypan and place on high heat.
Core the radicchio and cut the half into 8 small wedges. Place in the hot oil and sprinkle with salt. Cook for 1 minute on each side. Transfer to a large mixing bowl. Add lentils, walnuts, herbs, and cheese, if using. Stir gently to combine. Season to taste with salt and pepper. Serve warm or at room temperature.