Make the Raspberry Sauce: In a small bowl, combine the sugar and cornstarch until no lumps of cornstarch remain.
Add the sugar-cornstarch mixture, raspberries, and balsamic vinegar to a medium saucepan. Turn the heat to medium-high and bring to a boil. Lower heat to medium-low to gently simmer for 7 to 10 minutes, or until the fruit is very soft. Taste for sweetness and adjust as desired.
Place a fine mesh sieve over a medium bowl. Pour about a third of the mixture into the sieve. Using a silicone spatula, press the mixture into the sieve to catch seeds. Continue this process until all the seeds have been removed from the raspberry sauce. You should have a smooth, somewhat thick sauce.
Place the sauce in the refrigerator to cool while you make the chocolate cake. Or, the sauce can be made in advance up to 4 days.
Make the Easy Chocolate Cake: Preheat the oven to 350 degrees. Grease an 8” cake pan with nonstick spray or “cake goop/cake release”. Cover the bottom of the pan with a parchment circle and spray again. Set the pan aside.
In a medium bowl, add the flour, coca powder, baking soda, and salt. Sift the dry ingredients together with a whisk, or other sifter/sieve. Set aside.
In a large bowl, melt the butter in the microwave. Keep an eye on it so it does not splatter in your microwave. Add the oil, brown sugar and vanilla and whisk to combine.
Add both eggs and the sour cream, and whisk until combined.
Pour the flour mixture over the brown sugar mixture and using a wood spoon or silicone spatula, gently fold in the flour mixture.
Pour the hot coffee into the batter and gently incorporate. Scrape the batter into the prepared pan. Bake for 30 to 40 minutes, or until just done (a toothpick inserted in the center comes out with a few moist crumbs.)
Pull the cake out of the oven and allow it to stand at room temperature for 20 minutes. Invert onto a rack to completely cool, 1 to 2 hours. (The chocolate cake can be made up to 1 day in advance, or even frozen for up to 1 month.) Once the cake is out of the oven to cool, add your mixer bowl and whisk attachment for the Lavender Whipped Cream into the refrigerator.
Once the cake and sauce are cool, make the Lavender Whipped Cream: Place the whisk attachment onto a stand mixer. Alternatively, you can use a hand-held mixer
Add the cold whipping cream and confectioners’ sugar to the cold bowl. Mix on medium-high until the cream is starting to thicken before you crank your mixer to high, or you’ll likely splatter cream.
Add the food coloring and flavoring. Whip on high until light, thick, and fluffy. Taste and adjust sugar and lavender as desired.
To assemble: Gather your glasses for the trifles. Place a layer of cake into the bottoms of the glasses. Then layer with the sauce, then whipped cream. Continue the layering process. Top with fresh raspberries and mint leaves for garnish, if desired.
Enjoy immediately, or the prepared trifles can be refrigerated for up to 6 hours.