What is the test for a constructive amendment to a criminal charge?

"[A] constructive amendment occurs either where (1) an additional element, sufficient for conviction, is added, or (2) an element essential to the crime charged is altered." Dove, 884 F.3d at 146 (internal citation omitted). Our precedent has "consistently permitted significant flexibility in proof, provided that the defendant was given notice of the core of criminality to be proven at trial." United States v. Banki, 685 F.3d 99, 118 (2d Cir. 2012) (internal quotation marks omitted). Put differently, the indictment must alert a defendant to "the essence of a crime, in general terms," but need not specify "the particulars of how a defendant effected the crime." United States v. D'Amelio, 683 F.3d 412, 418 (2d Cir. 2012). So, to prevail on a constructive amendment argument, a defendant "must demonstrate that either the proof at trial or the trial court's jury instructions so altered an essential element of the charge that, upon review, it is uncertain whether the defendant was convicted of conduct that was the subject of the grand jury's indictment." United States v. Salmonese, 352 F.3d 608, 620 (2d Cir. 2003) (internal quotation marks omitted).