I usually find it difficult to check irreducibility of polynomials in $K[[X,Y]]$ ($K$ zero characteristic and algebraically closed). Does anyone know about generic methods that can be used ? And especially of ones that can be applied to polynomials like $XY-(X+Y)(X^2+Y^2)$ (I found it reducible by using Hensel's lemma after a suitable change of variable, if I did not make mistake).