Heat a 10-inch cast-iron skillet over medium-high heat. Add jalapeños; cook, turning occasionally, until skin is charred, 5 to 6 minutes. Place peppers in a small bowl, and tightly cover with plastic wrap. Let stand until cool enough to handle, about 15 minutes. Peel peppers, discarding skin and stem; finely chop peppers.
In a medium bowl, beat cream cheese and mayonnaise with a mixer at medium speed until almost smooth (small lumps may remain), 1 to 2 minutes, stopping to scrape sides of bowl as needed. Stir in Worcestershire, garlic powder, paprika, and mustard. Stir in chopped jalapeño, cheese, and pimientos until well combined. Serve immediately, or cover and refrigerate for up to 1 week.