1/4 cup mayonnaise
1/4 cup grainy mustard
1/4 cup extra-virgin olive oil
3 tablespoons fresh lemon juice
1 teaspoon finely grated lemon zest
1 garlic clove, crushed
2 teaspoons kosher salt
2 teaspoons fresh ground black pepper
1 pound thick asparagus, trimmed
In a shallow dish, whisk together the mayonnaise, mustard, oil, lemon juice, lemon zest, garlic, salt and pepper. Add the asparagus and turn to coat. Let stand at room temperature for 30 minutes.
Grill the asparagus over moderately high heat, turning occasionally, until the spears are tender and lightly blistered in spots, about 6 minutes. Serve the asparagus hot or at room temperature.