Melt butter in a medium fry pan or small pot.
Add blueberries, vanilla, pinch of salt, and pure maple syrup.
Simmer on medium heat for 5 minutes.
Make a slurry out of 1 tablespoon corn starch and 1 tablespoon of water.
Pour over summering blueberries and stir. This will thicken the compote.
Squeeze in the juice of 1/2 a lemon (it doesn't have to be the whole thing, just a bit depending on the tartness level you want!)
Simmer 3-5 more minutes until the compote is thickening up a bit.
Remove from heat and cool. It will thicken more as it sits for a few minutes!
Store extras in the refrigerator for up to 5 days.