A mechanism (10) includes a slide plate (32) having die openings (38) adapted to hold dies (42a, 42b) and slideable relative to a cooker/extruder (12). Rotary cutters (74, 174) are rotatably mounted relative to and moveable with the dies (42a, 42b). In one preferred form, a motor (76) can be connected and disconnected to the rotary cutter (74) aligned with the cooker/extruder (12) by moving a male coupling (96) within or out of a female coupling (108). In another preferred form, the rotary cutter (174) is mounted to and carried exclusively by a center shaft (180) fixed to the die (42a, 42b) and includes provisions (187, 191) located within a housing (183) for rotating the housing (183) on the center shaft (180). Thus, it is not necessary to shut down the cooker/extruder (12) to service or change the dies (42a, 42b) and/or the rotary cutters (74, 174). An annular wear plate (134) is sandwiched between the slide plate (32) and a frame element (18) having a central aperture (126) into which the barrel (14) of the cooker/extruder (12) is slideably received. A center plate (130) extends through the wear plate (134) and is received within the central aperture (126) and is fastened to the barrel (14). Mixer elements (59) are retained in the subpassageways (124) of the barrel (14) by the center plate (130) and can be removed through one of the die openings (38) when the die (42a, 42b) is removed therefrom and without removal of the barrel (14) from the frame element (18).