Step 1

For White Mac and Cheese Sauce, place potatoes in a steamer basket in a large saucepan. Add water to saucepan to just below basket. Bring to boiling. Steam, covered, 8 to 10 minutes or until very tender. Transfer potatoes to a blender; cool. Add the next five ingredients (through cayenne pepper). Cover and blend just until smooth. Season with salt. Transfer sauce to a saucepan; heat until thickened and warmed through.

Step 2

For the pasta, in a small saucepan bring vinegar and maple syrup to boiling. Remove from heat. Stir in radishes and garlic; cover and set aside.

Step 3

Prepare pasta according to package directions. Reserve 1 cup pasta cooking water. Drain pasta; return to pot. Add White Mac and Cheese Sauce; toss to coat. Add pasta cooking water a little at a time if needed to make creamy.

Step 4

Meanwhile, place asparagus, peas, and onion in a steamer basket in a large saucepan. Add water to saucepan to just below basket. Bring to boiling. Steam, covered, 4 to 6 minutes or until just tender.

Step 5

Add asparagus mixture to pasta mixture; toss to combine. Season with salt and pepper. Using a slotted spoon, top mac and cheese with radishes. Sprinkle with tarragon.