1. A household mixing and chopping apparatus with rotating cutting blades, such as a mincing machine or a grinder, comprising a base (10) including an electric motor (12) the output shaft (14) of which is positioned at the top (16) of the base, a bowl (18) which is releasably retained on the top (16) of the base and the bottom (20) of which accommodates a rotary shaft (22) one end of which carries rotating cutting blades (24) disposed in the bowl and the other end of which carries a driver (26) adapted to be coupled to the output shaft (14) of the motor, and comprising a switch disposed within the base (10) for controlling the motor, the actuating key (38) of said switch being disposed at the top of the base in the proximity of the bowl (18), and comprising a lid (28) removably mounted on the bowl (18) and having a skirt (30) extending downwardly around the bowl, the lower edge of said skirt being disposed perpendicularly above the actuating key (38), wherein said lid (28) may either have an upper position relative to the bowl (18) in which it covers the latter while it leaves the actuating key (38) of the switch in the inoperative position, or a lower position relative to the bowl in which the lower edge of the skirt (30) of the lid moves the key (38) into the operative position, characterized in that the outer surface of the sidewall (46) of the bowl (18) and the inner surface of the skirt (30) of the lid (28) are provided with means for mutual engagement therebetween, said means comprising at least one projection (48) carried on one of said surfaces and at least one seat (44) formed on the other surface and capable of resiliently receiving the projection (48) when the lid (28) is brought from the upper position into the lower position due to pressure applied thereto by the, user wherein the bowl (18) and the lid (28) will then form a closed vessel such that, if the user lifts the lid (28), he will at the same time lift the bowl (18), thereby decoupling the rotary cutting blades (24) from the shaft (14) of the motor.