Heat a pan on the stovetop on low and add your blackberries, honey, lemon juice and lavender. Mix and continuously crush the blackberries.
Turn heat up to medium and let the mixture start to boil. Continue to crush the blackberries so they are dissolved and the chunks are smaller. Don't turn the heat above medium. Keep stirring to keep your ingredients from burning.
Let the mixture simmer for about 10 minutes.
Remove from heat and let it cool.
Add it to an airtight container and refrigerate. As the mixture gets colder, it will come together more. If you make this the day before it will be perfect by the time you want to make the dessert. Give it at least an hour to chill in the fridge.