Line 8-inch square pan with foil or parchment, lightly buttered and extending over the pan’s edges.
Melt butter in medium saucepan over low heat. Add chocolate and stir by hand until melted and smooth.
Remove saucepan from heat. Stir in sugar and vanilla until combined.
Beat in eggs by hand, one at a time. Stir in garlic.
Add flour and stir energetically for 1 full minute, until batter loses its graininess, is smooth and glossy and begins to pull away from sides of saucepan.
Scrape batter into prepared pan and bake until centre feels almost set, about 30 minutes. Do not overbake.
Remove from oven. Let brownies cool completely in pan.
While carefully holding foil or parchment, lift block of brownie out of the pan. Cut into squares. Brownies will keep well up to 4 days and can be frozen up to 1 month.
Notes
*If black (fermented) is garlic unavailable, substitute roasted garlic.