For the brittle, preheat the oven to 375 degrees Fahrenheit. Mix together the sugar, cayenne, salt, and pumpkin seeds in a medium bowl. Whisk the egg white in a mixing bowl until foamy but not stiff. Fold the egg white into the pumpkin seeds.

Line a baking sheet with a silicone mat or parchment paper. Spread the brittle mixture thinly and evenly on the silicone mat and bake until the brittle turns completely golden brown, 20–30 minutes. Remove from oven and set aside to let cool. Break the brittle roughly into 2-inch shards.

For the vinaigrette, whisk the sugar and sherry vinegar together in a large mixing bowl or salad bowl until the sugar has dissolved. Add the shallots and thyme. Whisk in the canola, walnut, and pumpkin seed oils. Season with salt and pepper.

For the salad, put the greens into the bowl with the vinaigrette and toss well. Divide the greens between 6 individual plates and crumble blue cheese on top of each. Scatter shards of pumpkin seed brittle, chives, and chervil sprigs over the tops of the salads.