Poached Arctic Char with Basil-Tarragon Mayonnaise

INGREDIENTS

• 2 large egg yolks
• 2 fresh lemon juice
• 1 mustard powder
• 1/4 fresh basil leaves
• 1/4 fresh tarragon leaves plus 2 sprigs
• 1/4 extra-virgin olive oil plus more for serving
• 1 garlic clove, smashed
• 2 kosher salt plus more
• 6 6-ounce arctic char steaks, each about 1 1/4-inch thick
• 2 bunches asparagus (about 1 1/2 pounds), trimmed
• Flaky sea salt (such as Maldon)