You can do it with a scroll saw with the table tipped about 2-7 degrees. You sandwich the boards together with double sided tape and cut both at once. Different thickness boards will require experimenting to get the table angle right and you have to make the entire cut in one direction, but which way is decided by the direction of tilt of the table and which board becomes the heart and which becomes the hole for the heart. When you get it right the heart that is cut in one board will fit perfectly into the tapered hole in the other board. I haven't done this in years, so don't remember the fine details, but it woks great when the adjustments are correct. For a heart, make your blade entry hole in the bottom of the V at the top of the heart and make it just barely large enough to get the blade through it. It will be almost invisible in the final assembly. I liked to make the heart stand slightly proud of the board surface so I could sand it perfectly flush. If you do this and both boards are exactly the same thickness, there will be a slight indentation of the back side of the heart. You can work to make the boards flush or the heart slightly proud of the surface by changes of about 1/2 degree of the table.
Central North Carolina