1 Preheat the oven, put together the baking dish: Preheat the oven to 375℉.
2 Slice the greens: Utilizing a mandoline or a really sharp chef’s knife, reduce the parsnips and carrots diagonally into slices about 1/8-inch thick. Halve the fennel, then reduce into slices about 1/8-inch thick.
3 Sauté the aromatics and fennel: Soften the butter in a sauté pan over medium-high warmth. When the butter is foamy, add the shallots, and prepare dinner till gentle and translucent, about 3 minutes. Add the fennel, and prepare dinner till simply tender, 4 minutes. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Stir within the garlic and thyme, and prepare dinner till fragrant, one other 30 seconds.
4 Layer the greens: Grease a big (2 quart) gratin dish or a 9-x-13-inch glass baking dish with butter. Layer half of the parsnips within the gratin dish, sprinkle with a pinch of salt and a grind of black pepper.
Prime with half of the carrots, and season with one other pinch of salt and grind of black pepper. Scatter half of the fennel combination on prime of the carrots.
Repeat with the remainder of the parsnips and carrots, ending with the remaining fennel combination. Put aside.
5 Start the béchamel: You will want two sauce pans, one small and one medium.
In a small sauce pan set over medium-low warmth, add the milk and cream.
In a medium saucepan set over medium warmth, add the butter. When the butter foams, whisk the flour into the melted butter, and prepare dinner till nutty smelling and light-weight golden in shade, about 3 minutes.
6 Add the milk to the roux: Slowly whisk the nice and cozy milk and cream somewhat bit at a time into the butter and flour combination (roux) till mixed. The sauce must be easy.
Convey the béchamel to a simmer, keeping track of the warmth and stirring regularly to forestall scorching. It should actually begin to thicken because it simmers.
Cut back the warmth to medium-low, and simmer till the sauce is thick and coats the again of a spoon, about 4 minutes.
7 Take away from warmth and add the cheese: Take away the béchamel from the warmth and whisk within the blue cheese a couple of crumbles at a time. Season the sauce with salt, pepper, nutmeg, and a pinch of cayenne, if you would like somewhat warmth. Style and alter the seasoning, if desired.
8 Add the béchamel to the greens: Pour the nice and cozy béchamel excessive of the greens within the gratin dish and let sit for at the least quarter-hour to permit the sauce to soak into the greens.
Scatter the pecans excessive of the gratin. (The gratin will be made forward up thus far, then refrigerated till able to bake.)
9 Cowl and bake: Snugly cowl the gratin with foil and bake for 45 minutes. Uncover and bake for one more 20 minutes, or till the gratin is golden brown and bubbly, and the greens are tender when pierced with a knife.
10 Serve: Let relaxation 20 minutes earlier than serving.