Queen's Gambit Declined - semi-Slav - Koomen variation
1. d4 d5 2. c4 e6 3. Nc3 c6 4. Nf3 dxc4 5. a4 Bb4 6. e3 b5 7. Bd2 Qe7
White plays the queen's pawn to d4. Black pushes the queen's pawn to d5. White moves the c-pawn to c4.
Black moves the king's pawn to e6. White develops the knight to c3. Black plays the c-pawn to c6.
White moves the knight to f3. Black captures on c4 with the queen's pawn. White advances the a-pawn to a4.
Black develops the dark-squared bishop to b4. White plays the king's pawn to e3. Black pushes the b-pawn to b5.
White develops the dark-squared bishop to d2. Black deploys the queen to e7.