-Heat the oven to 450°F.
-Cut 1 pound of potatoes in quarters lengthwise, then in eights.
-Toss with 1 TBS extra virgin olive oil in a large bowl and a generous pinch of sea salt and pepper.
-Spread the potatoes on a large baking sheet and bake for 10-15 minutes or until barely tender.
-Meanwhile, trim the tops and bottoms of the radishes, and quarter them lengthwise.
-Peel 1 watermelon radish.
-Cut into slices, then large matchsticks.
-Trim off the top and bottom of 1 fennel bulb and slice in half lengthwise, then quarter each half and cut the quarters into pieces about 1-inch-wide.
-Toss the fennel pieces and radishes in the bowl with another TBS of olive oil and salt and pepper.
-When the potatoes are just beginning to get tender, spread the radishes and fennel on the baking sheet and toss to combine.
-Return the vegetables to the oven and roast for an additional 10 to 15 minutes or until the fennel and radishes are tender and juicy but not yet soft.
-While they are roasting, heat ¼ cup unsalted butter in a small saucepan over medium heat for 4 to 6 minutes or until it melts and then browns.
-Remove from the heat and carefully whisk in the following:
½ lemon juiced, about 1½ TBS
½ tsp Dijon mustard
½ tsp maple syrup
-When the vegetables are done, toss with the sauce and spread on a platter or in a bowl.