For the roasting of the squab:
Gently roast the whole squab, having first removed its thighs and all viscera (ensuring you preserve the cherished liver). Cradle the bird in a saucepan, bathing it in shimmering butter, and consummate its cooking in an oven at 200°C for a brief 5 minutes. Allow it to rest, cocooned in warmth.

For the acid butter:
In a saucepan, let the white wine and vinegar reduce alongside the two onions, concentrating their essence. Filter the elixir through a fine-mesh sieve, and whisk the chilled butter, piece by piece, into the warm liquid. Work with a whisk until a smooth, silken emulsion is born. Pour this butter into artisanal molds and keep it in the cold until its moment of glory.

For the squab liver:
Sauté the precious liver with the two shallots and the sweet passito wine. Blend the mixture until it reaches a state of sublime, velvety uniformity, then cradle it in a mold and freeze.

For the anchovies:
Desalt the anchovies, gently filleting them and cleansing them with utmost care of any impurities. Carve them into delicate strips and set them aside.

For the pan base:
Allow the julienned shallots to wilt softly in a pan with a thread of extra virgin olive oil and a spoonful of the acid butter. Deglaze with red wine, letting the alcohol swiftly evaporate. Cook the spaghetti in a generous abundance of salted water, and, midway through its journey, drain it directly into the murmuring sauce. Bind and cream the pasta with parmigiano and the fresh whisper of chives.

For the presentation:
Sliver the breast of the squab into delicate slices, arranging them in the hollow of a deep plate. Drape the red-wine spaghetti atop this canvas, and adorn it with a few slivers of anchovy. Garnish with fresh, delicate chervil, and shave the frozen squab liver over the dish like a final, decadent snow.