1. Whisk flour, baking powder, and salt in medium bowl and set aside.
2. Melt 1/4 cup butter in a small, heavy saucepan over medium-low heat. Add cocoa powder and whisk until no lumps remain, then slowly add milk, whisking constantly, until mixture is thickened and uniform. Remove from heat and whisk in brown sugar, egg, and vanilla extract until mixture is smooth and uniform. Pour cocoa mixture over flour mixture and stir until dry and wet ingredients are thoroughly combined. Stir in chocolate chips.
3. Melt about 1/4 teaspoon butter in a large nonstick skillet or griddle over medium-low heat and swirl to coat cooking surface. Using about 1 tablespoon. batter per 2-inch pancake, add batter to skillet, and cook until edges look set and bubbles appear across pancakes, 1 to 1 1/2 minutes. Flip pancakes and cook until center is cooked through and second side is lightly browned, about 1 minute longer.
4. Repeat with remaining batter, using an additional 1/4 teaspoon butter for each new batch of blini. Top each blini with 1 teaspoon mascarpone and 1 scant teaspoon of Two Raspberry spread, and serve. If you're not serving the blini fresh from the pan, place on a baking sheet and keep them warm in a 200 degrees F oven for about 15 minutes.