Step 1: Pour your whipping cream into your mixer with whisk attachment. Whip on high for about 1 minute, add your sugar and vanilla and continue to mix until a semi-firm peaks form.
Step 2: Toasted pecans:
Place pecans on a baking sheet and toast in a 350 degree F. oven for 10-15 minutes until aromatic. Let cool.
Step 3: Assembly:
Place in your mason jar your brownie circle, your whipped cream, chocolate syrup and pecans, repeat one more time until you've reached the top.
Step 4: If you are going to serve them later, leave room at the top to be able to put the lid on until ready to serve.
Step 5: When ready to serve, top with whipped cream, chocolate syrup and pecans.