Pick about 8-10 cups of fresh blooms. This isn't an exact science but go for 1-part dandelions to 2-parts forsythia blooms. You can just make this with forsythia blooms, but I like the pollen and color boost the dandelions give the jelly.
I don't bother to take the bottoms off the forsythia as they just taste "plant-y" but I do remove the green bottoms of the dandelions since they're bitter. Cut off the green part with kitchen scissors and keep the petals, pollen, and fluff.
Pour enough boiling water over the flowers to cover them, at least 4 cups. The more water you add, the weaker the tea will be and, therefore, the less golden flavor the jelly will have in the end.
Steep the water and flowers for 4 hours or overnight.
Strain through cheesecloth to remove the flower parts, leaving a lovely, golden tea.
Put tea, lemon juice, and the contents of a box of pectin into a large saucepan. Add vanilla seeds—you can also add the vanilla bean for the boiling. If you do that, simply remove the bean before you put the jelly into jars. You can leave the bean in one jar for aesthetics and gift it to someone extra special.
Bring to a boil and add the honey.
Bring back to a boil and boil for about 2 minutes. Ladle into hot, prepared jelly jars, leaving 1/4" head-space and assemble the lids.
Process in a water bath canner for 10 minutes.