Pub-Style Burger Sauce

Whisk all ingredients together in bowl.

JUICY PUB-STYLE BURGERS WITH CRISPY SHALLOTS AND BLUE CHEESE
Heat 1⁄2 cup vegetable oil and 3 thinly sliced shallots in medium saucepan over high heat; cook, stirring frequently, until shallots are golden, about 8 minutes. Using slotted spoon, transfer shallots to paper towel–lined plate, season with salt, and let drain until crisp, about 5 minutes. (Cooled shallots can be stored at room temperature for up to 3 days.) Top each burger with 1 ounce crumbled blue cheese before transferring to oven. Top with crispy shallots just before serving.

JUICY PUB-STYLE BURGERS WITH SAUTÉED ONIONS AND SMOKED CHEDDAR
Heat 2 tablespoons vegetable oil in 12-inch skillet over medium-high heat until just smoking. Add 1 thinly sliced onion and 1⁄4 teaspoon salt; cook, stirring frequently, until softened and lightly browned, 5 to 7 minutes. Top each burger with 1 ounce grated smoked cheddar cheese before transferring to oven. Top with onions just before serving.

JUICY PUB-STYLE BURGERS WITH PEPPERED BACON AND AGED CHEDDAR
Adjust oven rack to middle position and heat oven to 375 degrees. Arrange 6 bacon slices on rimmed baking sheet and sprinkle with 2 teaspoons coarsely ground pepper. Place second rimmed baking sheet on top of bacon and bake until bacon is crisp, 15 to 20 minutes. Transfer bacon to paper towel–lined plate and cool. Cut bacon in half crosswise. Top each burger with 1 ounce grated aged cheddar cheese before transferring to oven. Top with bacon just before serving.

JUICY PUB-STYLE BURGERS WITH PAN-ROASTED MUSHROOMS AND GRUYÈRE
Heat 2 tablespoons vegetable oil in 12-inch skillet over medium-high heat until just smoking. Add 10 ounces trimmed and thinly sliced cremini mushrooms, 1⁄4 teaspoon salt, and 1⁄4 teaspoon pepper; cook, stirring frequently, until browned, 5 to 7 minutes. Add 1 minced shallot and 2 teaspoons minced thyme and cook until fragrant. Remove skillet from heat and stir in 2 tablespoons dry sherry. Top each burger with 1 ounce grated Gruyère cheese before transferring to oven. Top with mushrooms just before serving.