Place 1-1/4 cups walnuts on a baking sheet. Bake in a preheated 350-degree oven for 7 to 9 minutes or until toasted. Coarsely chop 1 cup of the walnuts. Finely grind remaining walnuts; set aside. Increase oven temp to 375.
In a large bowl combine flour, finely ground walnuts, baking powder, baking soda, and salt. With a pastry blender, cut in the butter until the mixture resembles coarse meal. Stir in the Gruyere, 1 cup coarsely chopped walnuts, and thyme.
Make a well in the center of this mixture. In a bowl combine egg, buttermilk, honey, and mustard; add all at once to the flour mixture. Stir with a fork just until moistened.
Turn the dough out onto a lightly floured surface. Knead by folding and gently pressing it for 10 to 12 strokes or until nearly smooth. Divide in half. Pat or lightly roll each half to a 3/4-inch-thick circle, about 6 inches in diameter. Cut each circle into 8 triangles.
Place triangles 2 inches apart on a greased baking sheet. Bake for 18 to 20 minutes or until golden brown.
Transfer scones to a cooling rack. If desired, top with more cheese, walnuts, and thyme. Serve warm.