Espresso coffee machine comprising: - a main boiler , configured for producing hot water and steam; - at least one dispensing group , configured for producing coffee and physically and functionally independent from said main boiler ; - a secondary boiler physically and hydraulically connected to each dispensing group , said secondary boiler being configured to keep the water for dispensing coffee at a predetermined temperature value checked by a temperature probe ; - a main water inlet circuit for inletting water from the water supply network, hydraulically connected to the main boiler and to the secondary boiler of each dispensing group , said main water inlet circuit comprising at least one booster pump that applies a predetermined pressure value to the water; and - an electronic control unit , the espresso coffee machine being characterised in that it comprises: - a pressure sensor , provided with a sensitive element enclosed within the secondary boiler of each dispensing group and placed in contact with the water; - a bypass circuit hydraulically connected, at a first end, to said main water inlet circuit upstream of the booster pump and, at the opposite end, to each dispensing group ; and - at least one two-way proportional valve , arranged on the bypass circuit and electronically controlled by the electronic control unit , said two-way proportional valve being configured to recirculate a part of delivery flow of said booster pump on said main water inlet circuit and upstream of the booster pump , in order to maintain a certain coffee extraction pressure value in each dispensing group set in real time by the pressure sensor . - a main boiler , configured for producing hot water and steam; - at least one dispensing group , configured for producing coffee and physically and functionally independent from said main boiler ; - a secondary boiler physically and hydraulically connected to each dispensing group , said secondary boiler being configured to keep the water for dispensing coffee at a predetermined temperature value checked by a temperature probe ; - a main water inlet circuit for inletting water from the water supply network, hydraulically connected to the main boiler and to the secondary boiler of each dispensing group , said main water inlet circuit comprising at least one booster pump that applies a predetermined pressure value to the water; and - an electronic control unit , - a pressure sensor , provided with a sensitive element enclosed within the secondary boiler of each dispensing group and placed in contact with the water; - a bypass circuit hydraulically connected, at a first end, to said main water inlet circuit upstream of the booster pump and, at the opposite end, to each dispensing group ; and - at least one two-way proportional valve , arranged on the bypass circuit and electronically controlled by the electronic control unit , said two-way proportional valve being configured to recirculate a part of delivery flow of said booster pump on said main water inlet circuit and upstream of the booster pump , in order to maintain a certain coffee extraction pressure value in each dispensing group set in real time by the pressure sensor . <EOS>