A gasket assembly (20) and method for forming the gasket assembly (20) for sealing two mating surfaces (46,48) over a complex geometrical contact region. The gasket assembly (20) is formed by a hollow silicone rubber tube (22) having a naturally straight configuration but easily bent into complex configurations without kinking. The tube (22) is filled with a curable liquid rubber compound (30) and then the ends (24,26) of the tube (22) are joined in end-to-end fashion to form a continuous loop. The joined ends (24,26) of the tube (22) can be reinforced with a connector (34,134) and then locally cured on a preliminary operation so that the liquid rubber compound (30) does not escape. The tube (22) is then laid up in a mold (40) having a complex geometrical feature (42) which replicates the complex geometrical contact region of the two mating surfaces (46,48) to be subsequently sealed. With the tube (22) held stationary in the mold form (40), the entrapped liquid rubber compound (30) is cured using a heat source (44) or other suitable curing accelerant. Once fully cured, the core of rubber compound (30′) takes a set in the complex geometrical form, and resists straightening of the tube (22) so as to hold the gasket assembly (20) in the complex geometrical shape required to later seal the mating surfaces (46,48). The tube (22) and core of cured rubber compound (30′) may be selected of materials which possess different durometers.