Step 1

Season brisket all over with ground pepper and ¼ cup Diamond Crystal or 2 Tbsp. plus 2 tsp. Morton salt, rubbing into the grain. Wrap tightly in plastic and chill at least 3 hours and up to 3 days.

Step 2

Place a rack in lower third of oven; preheat to 275°. Heat schmaltz in a large roasting pan set over 2 burners on high. Unwrap brisket; cook, reducing heat if needed, until browned, 7–10 minutes per side. Transfer to a baking sheet.

Step 3

Reduce heat to medium-high. Add onions, carrots, and celery to pan; season with salt. Cook, stirring occasionally, until browned and just softened, 15–18 minutes. Add wine, bring to a boil, and cook until evaporated, 8–10 minutes. Add garlic, thyme, bay leaves, and peppercorns. Pour in broth to come about halfway up sides of pan, then bring to a boil. Nestle brisket into aromatics and cover tightly with foil; braise in oven until meat is very tender but still holds its shape, 2–3 hours. Let cool, then chill at least 8 hours and up to 2 days.

Step 4

Preheat oven to 250°. Remove solidified fat from surface of braising liquid; discard. Transfer brisket to a platter. Strain braising liquid into a large measuring glass; discard solids. Return liquid to pan and cook over medium-high heat, stirring occasionally, until reduced by half, velvety and intensely flavored, but not overly salty, about 30 minutes.

Step 5

Return brisket to pan, cover with foil, and heat in oven until warmed through, 60–90 minutes. Transfer to a cutting board and slice against the grain. Arrange on platter and pour braising liquid over.