You can make bigger or smaller cookies than I described, but larger cookies will definitely need more jam. Just be careful it doesn't drip over the sides, as it will bubble and spread while baking and can burn when it hits the cookie sheet.
I baked my cookies for 20 minutes, but then I find my propane oven works a little differently than my hotter burning gas oven (even though the thermometer reads the same). You do want these to crips and slightly brown, but not burn. Check them after fifteen minutes and go a couple of minutes at a time from there.
When shaping the cookies you might want to keep some warm water nearby and dip your fingers periodically so they don't get too sticky and coated with dough!