1) Start oats the night before by heating water and stirring it into oats. Let sit overnight, covered.
2) THe next morning, drain oats of any extra water. Peel and grate apple and squeeze lemon juice into grated apple. Then stir apple into oats along with mashed banana.
3) To make the syrup, combine ingredients in a small pot over medium heat and cook until sugar is dissolved and berries are just starting to break down, just a few minutes. Kill the heat and let cool slightly.
4) Divide muesli between four bowls. Top with greek yogurt.
5) Spoon berry syrup over the muesli and top with toasted almonds and a drizzle of honey. Garnish with mint.
Can be made 30 minutes in advance.
For almonds, add slivered almonds to a dry pan and toast over medium-low heat until they are fragrant, about five minutes.