In a small saucepan, warm the heavy cream until hot. Whisk in the crushed red pepper, sugar and one-third of the blue cheese until melted. Let cool completely, then whisk in the sour cream and the remaining cheese. Season the dressing with salt. Prepare the broccoli

In a large saucepan of salted boiling water, blanch the broccoli until crisp-tender, about 2 minutes. Drain well and spread on a large baking sheet to cool.

In a blender, combine the vinegar, harissa, lemon zest and juice, soy sauce, mustard and Sriracha and puree. With the blender on, gradually add the olive oil until incorporated. Transfer the vinaigrette to a medium bowl and stir in the shallots. Season with salt and pepper.

In a medium skillet, melt the butter. Add the cereal and 1½ teaspoons of the harissa vinaigrette and cook over moderately high heat, stirring, until lightly browned, about 3 minutes. Season with salt and transfer to a paper towel–lined plate to drain.

Light a grill or preheat a grill pan. In a large bowl, toss the broccoli with half of the remaining vinaigrette and season with salt. Grill the broccoli over moderately high heat, turning occasionally, until lightly charred all over, about 5 minutes. Transfer to a plate.

Spread the blue cheese dressing on a platter and scatter the broccoli on top. Garnish with the spiced crispies and serve, passing the remaining harissa vinaigrette at the table.