Preheat and prepare the roots: Preheat the oven to 200°C / 400°F (convection if you have it). Toss the peeled and wedged carrot, parsnip and beet (≈200 g) with 1 tsp olive oil, a pinch of salt and a few grinds of black pepper. Spread them in a single layer on a rimmed baking sheet. Roast for 30–35 minutes, turning once halfway through, until edges are deeply caramelized and interiors are tender. WHY: High dry heat promotes caramelization which concentrates the roots' natural sugars and creates a sweet, nutty counterpoint to the savory cod.

Make the miso-butter glaze: While the roots roast, soften 1 tbsp unsalted butter at room temperature (or microwave 5–7 seconds). In a small bowl, combine the softened butter and 1 tbsp white miso paste until smooth. Taste and add a light pinch of black pepper; do not add extra salt — miso is already salty. WHY: Combining miso with butter mellows miso’s sharpness and creates a glossy glaze that carries flavor and helps the fish brown without drying.

Prep the broccolini dressing: In a small bowl whisk together 1 tsp Dijon mustard, 1 tsp toasted sesame oil, 1 tsp soy sauce (or tamari), the minced garlic clove, and the juice of 1/2 lemon (about 1 tbsp). If the dressing seems thick, add 1–2 tsp warm water and whisk to loosen. Reserve. WHY: The mustard emulsion binds the sesame oil and soy while lemon brightens and lifts the dressing so it cuts the richness of the miso butter and roasted roots.

Blanch the broccolini (optional but recommended): Bring a medium pot of salted water to a rolling boil. Add the 100 g broccolini and blanch 60–90 seconds until vibrant green and just tender. Immediately transfer to an ice bath or very cold water to stop cooking and preserve color. Drain and pat dry. WHY: Blanching shortens pan time and ensures even cooking and vivid color; shocking stops carryover cooking so the broccolini won't over-soften in the pan.

Heat the pan for the cod: Pat the cod dry with paper towels and season very lightly with salt and a good grind of black pepper. Heat a 10–12 inch skillet (preferably stainless steel or cast iron) over medium-high until hot. Add 1 tsp neutral oil and swirl. WHY: A very hot pan gives immediate contact sear, developing a golden crust that adds both flavor and texture and helps keep the interior moist.

Pan-sear the cod: Place the cod in the hot pan and let it sear undisturbed for 2–3 minutes, until the underside is golden and releases easily from the pan. Flip carefully. Reduce heat to medium-low, add the miso-butter mixture to the pan beside the fish and, using a spoon, baste the top of the fillet with the melted miso butter for 30–60 seconds while the fish finishes cooking. Cook until the fish is just opaque through the center and flakes easily, about another 2–3 minutes depending on thickness. WHY: Starting on high heat forms a flavorful crust; lowering the heat and basting with miso-butter prevents the sugars in miso from burning while infusing the fish with savory, silky flavor.

Rest the fish briefly: Transfer the cooked cod to a plate and let it rest 2 minutes — loosely tent with foil if desired. While the fish rests, any residual fat in the pan is perfect for finishing the broccolini. WHY: Resting allows juices to redistribute and the glaze to set, so the fillet remains moist and slices cleanly.

Finish the broccolini: Return the skillet to medium heat and add a drizzle (about 1 tsp) neutral oil or use the pan's leftover flavored fat. Add the blanched broccolini and toss briefly (1–2 minutes) to pick up pan fond and to warm. Remove from heat, toss immediately with the mustard-sesame dressing, and adjust seasoning with salt and pepper to taste. WHY: A quick warm in the hot pan develops a touch of char and marries the dressing into the vegetable for balanced flavor and attractive texture.

Plate and finish: On a warm plate arrange the roasted root medley as a base, place the miso-butter cod on top or alongside, and arrange the dressed broccolini for color contrast. Finish with a squeeze of the remaining lemon over the fish (about ½ tsp) to brighten, and — if you have it — a small sprinkle of toasted sesame seeds or microgreens. WHY: Acid at the end brightens flavors and balances the richness of the miso butter; plating contrasts textures and color for a restaurant-quality presentation.

Serve immediately: Serve while hot to enjoy the contrast of warm roasted roots, silky miso-butter cod, and crisp-tender broccolini. WHY: These components are at their best hot — the glaze is glossy and the broccolini retains bite.