I claim the ornamental design for a stovetop mini oven, as shown and described.
FIG. 1 is an exploded top perspective view of a stovetop mini oven, showing a pan with a raised roasting plate exploded away from a cover with a temperature gauge and a knob;
FIG. 2 is an exploded bottom perspective view thereof, showing the pan with a recessed heat disbursement plate on a bottom of the pan exploded away from the cover having a temperature gauge stem on a bottom side thereof;
FIG. 3 is a top perspective view thereof, illustrated in an assembled position;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof;